ALBERT

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Deepika Rani, Lakhan Bainsla, K.G. Suresh, Aftab Alam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this report, structural, electronic, magnetic and transport properties of quaternary Heusler alloys CoRuMnGe and CoRuVZ (Z = Al, Ga) are investigated. All the three alloys are found to crystallize in cubic structure. CoRuMnGe exhibits L2〈sub〉1〈/sub〉 structure whereas, the other two alloys have B2-type disorder. For CoRuMnGe and CoRuVGa, the experimental magnetic moments are in close agreement with the theory as well as those predicted by the Slater-Pauling rule, while for CoRuVAl, a relatively large deviation is seen. The reduction in the moment in case of CoRuVAl possibly arises due to the anti-site disorder between Co and Ru sites as well as V and Al sites. Among these alloys, CoRuMnGe has the highest 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si63.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉C〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 of 560 K. Resistivity variation with temperature reflects the half-metallic nature in CoRuMnGe alloy. CoRuVAl shows metallic character in both paramagnetic and ferromagnetic states, whereas the temperature dependence of resistivity for CoRuVGa is quite unusual. In the last system, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si64.svg"〉〈mrow〉〈mi〉ρ〈/mi〉〈/mrow〉〈/math〉 vs. T curve shows an anomaly in the form of a maximum and a region of negative temperature coefficient of resistivity (TCR) in the magnetically ordered state. The 〈em〉ab initio〈/em〉 calculations predict nearly half-metallic ferromagnetic state with high spin polarization of 91, 89 and 93% for CoRuMnGe, CoRuVAl and CoRuVGa respectively. In the case of CoRuMnGe, the XRD analysis reveals that the Co and Ru sites are equally probable. Hence, to investigate the electronic properties of the experimentally observed structure, the Co-Ru swap disordered structures of CoRuMnGe alloy are also simulated and it is found that the disordered structures retain half-metallic nature, high spin polarization with almost same magnetic moment as in the ideal structure. Nearly half-metallic character, high 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si65.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉C〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 and high spin polarization make CoRuMnGe alloy promising for room temperature spintronic applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Alessandra Manzin, Riccardo Ferrero〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a GPU-parallelized 2.5D micromagnetic solver for the efficient calculation of the magnetization configuration and hysteresis loop of 3D random distributions of magnetic thin-film objects, strongly interacting in the space. To well-reproduce complex shapes, the exchange field is calculated with a finite difference approach able to handle non-structured meshes. To enable the treatment of many objects, the magnetostatic field is locally separated into two contributions: an internal and an external one. The first term includes the magnetostatic interactions internal to each object and is obtained by numerically solving the Green’s integral equation. The second term describes the inter-object magnetostatic interactions and it is determined by approximating each object as a collection of magnetic dipoles, associated with mesh elements. The accuracy and computational efficiency of the solver are analysed by comparison to a standard 3D-FFT code and to a reference code, where all the magnetostatic field terms are evaluated by numerically solving the Green’s integral equation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Shivani Sharma, Poonam Yadav, Tusita Sau, Premakumar Yanda, Peter J. Baker, Ivan da Silva, A. Sundaresan, N.P. Lalla〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉SrTi〈sub〉0.5〈/sub〉Mn〈sub〉0.5〈/sub〉O〈sub〉3〈/sub〉 (STMO) is a chemically disordered perovskite having random distribution of Ti and Mn over 1〈em〉b〈/em〉 site. Striking discrepancies about the structural and magnetic properties of STMO demand detail analysis which is addressed. To explore the magnetic ground state of STMO, static and dynamic magnetic properties were studied over a broad temperature range (2–300 K). The 〈em〉dc〈/em〉 and 〈em〉ac〈/em〉 magnetization shows a cusp like peak at 〈em〉T〈sub〉f〈/sub〉〈/em〉 ~ 14 K, which exhibits field and frequency dependence. The thermoremanent magnetization is characterized by using stretched exponential function and characteristic time suggests the existence of spin clusters. Also, the other features observed in magnetic memory effect, muon spin resonance/rotation and neutron powder diffraction confirm the existence of cluster spin glass state in STMO, rather than the long-range ordered ground state. Intriguingly, the observed spin-relaxation can be attributed to the dilute magnetism due to non-magnetic doping at Mn-site and competing antiferromagnetic and ferromagnetic interactions resulting from the site disorder.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 491〈/p〉 〈p〉Author(s): M. Pugaczowa-Michalska〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The neutron-scattering measurements and the observation of hyperfine interaction of nuclear moments in Pd〈sub〉2〈/sub〉MnGe alloy have prompted a study of disorder in this compound by the density functional theory methods. Two approaches: the coherent-potential approximation (CPA) and supercell modelling were used to gain microscopic insight into the electronic and magnetic properties of disordered Pd〈sub〉2〈/sub〉MnGe. The influence of disorder between Pd and Mn sublattices in Pd〈sub〉2〈/sub〉MnGe on the magnetic moment of Mn atoms is discussed. The presented CPA studies have shown that the small disorder in Pd〈sub〉2〈/sub〉MnGe (between the Pd-Mn sublattices of the L2〈sub〉1〈/sub〉 structure) does not well describe the experimental evidence of antiparallel alignment of magnetic moment of Mn at positions (A,C) and B positions. However, the appearance of antiparallel moment of Mn at positions A and B was predicted for the Pd〈sub〉2〈/sub〉MnGe in the frames of 128-atoms supercell calculations. The generalized gradient approximation (GGA) has been the main basis for the presented supercell first-principles electronic structure calculations. The magnetic moment of Mn(A,C) is found to be small and negative value of −0.177 µ〈sub〉B〈/sub〉. The values of magnetic moment of Mn(B) are between 3.6 µ〈sub〉B〈/sub〉 and 3.72 µ〈sub〉B〈/sub〉. The results obtained for the supercell calculations are consistent with available experiments in the literature. The results of presented calculations in the supercell approach have shown that the disordered Pd〈sub〉2〈/sub〉MnGe can be predicted as a mixture of several supercells.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885319308285-ga1.jpg" width="343" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 491〈/p〉 〈p〉Author(s): Anupam Maity, Subha Samanta, Ramaprasad Maiti, Soumi Chatterjee, Debasish Biswas, Dipankar Chakravorty〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanodimensional silica-based spin glasses of compositions xCoO-(100-x)SiO〈sub〉2〈/sub〉 with x having values 20 and 30 were synthesized by sol-gel method within mesoporous silica SBA-15 (Santa Barbara Amorphous-15) having a pore diameter ~5.5 nm. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of both Co〈sup〉2+〈/sup〉 and Co〈sup〉3+〈/sup〉 species within the glasses. This caused electronic conduction in this amorphous system. The nanoglasses exhibited resistivity values at room temperature which were about three orders of magnitude lower than those of the corresponding bulk glasses. The resistivity data for the nanodimensional glasses on analysis confirmed the conduction to arise due to small polaron hopping between the localized states represented by these ions with an activation energy in the range 0.08–0.07 eV. The inter-site separation values extracted from the analysis of the resistivity data were found to lie in the range 6.7–6.6 Å. The values of magnetodielectric (MD) parameter for the different nanocomposites were rather large with the highest value found to be in the range 523–49% for the frequencies 1 kHz and 1 MHz in case of nanocomposite with a glass composition 30CoO-70SiO〈sub〉2〈/sub〉. The dissipation factor for the samples was, however, in the range 0.3–1.6. By using suitable measuring frequency the dissipation factor could be brought down to a value less than 1.0 with the M.D. parameter exhibiting values in the range 10–49%. The results were fitted to Catalan’s model based on two dielectrics with different resistivity values connected in series. The satisfactory fit of the experimental data to the theoretical model based on a negative magnetoresistance of the nanoglasses leads to the conclusion that an enhancement of spin polarized electron hopping is the reason behind this effect. The results obtained should be further explored to find applications of these materials as magnetic sensors as well as magnetically controlled supercapacitors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 491〈/p〉 〈p〉Author(s): Doan Quoc Khoa, Bui Dinh Hoi, Tran Cong Phong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, we theoretically address the transverse Zeeman magnetic field effects on the frequency-dependent dynamical dielectric function of phosphorene including the refractive index and the absorption coefficient. An effective Hamiltonian model beyond the continuum approximation is employed to obtain the electronic dispersion energy. The linear response theory is applied to calculate the dynamical dielectric function at a certain temperature along both armchair and zigzag edges. Our numerical calculations show that, independent of the direction, the refraction (absorption) intensity decreases (increases) with the optical frequency at all magnetic field strengths. Moreover, we find out that the refraction and absorption processes along the armchair edge do not change after a critical magnetic field and this critical point increases with the optical frequency stemming from the spin-splitting effects. As for the zigzag edge, however, there is a little to no change for these processes with the magnetic field. Further, we observe that, on the average, the dominant contribution to the total magnetic field-dependent dynamical dielectric function comes from the armchair edge originating from the smaller (larger) carrier effective mass (velocity) than the zigzag edge. Tuning the optical responses of phosphorene with the transverse Zeeman magnetic field is useful for practical spintronic applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 491〈/p〉 〈p〉Author(s): M.Kh. Hamad, Y. Maswadeh, Kh.A. Ziq〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigate the effect of Ni-substitution on the crystalline structure and the critical behavior of Nd〈sub〉0.6〈/sub〉Sr〈sub〉0.4〈/sub〉Mn〈sub〉1−x〈/sub〉Ni〈sub〉x〈/sub〉O〈sub〉3〈/sub〉 〈em〉(0.00〈/em〉 ≤ 〈em〉x〈/em〉 ≤ 〈em〉0.20)〈/em〉 perovskite. X-ray diffraction patterns revealed that the major phase in all samples is the orthorhombic structure with space group 〈em〉Pnma〈/em〉. Rietveld refinement revealed a linear reduction in the lattice parameters along with monotonic reduction in the 〈em〉O2-Mn-O2〈/em〉 angel with increasing Ni concentration. The modified Arrott plots and the Kouvel-Fisher method have been used to analyze the magnetization isotherms near the paramagnetic to ferromagnetic (PM-FM) phase transition. The obtained critical exponents (β, γ and δ) revealed that the 〈em〉Ni〈/em〉-free sample is consistent with 3D-Heisenberg like behavior. However, upon Ni-substitution, the critical exponents exhibit a mean field like behavior. The reliability of the obtained critical exponent (β, γ, and δ) values have been confirmed by the universal scaling behavior of the isothermal magnetization near the transition temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): N.V. Ter-Oganessian, S.A. Guda, V.P. Sakhnenko, V. Ohanyan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fluorides in general are characterized by big variety of crystal structures, whereas those containing transition metals also often show sizable magnetic properties. The tendency of fluorine to form linear chain structures in many cases results in low-dimensional magnetism. Despite the plethora of magnetic phenomena in fluorides, their magnetoelectric properties are less studied than those of oxides. In the present work we theoretically study the magnetic and magnetoelectric properties of spin-chain compounds CaFeF〈sub〉5〈/sub〉 and SrFeF〈sub〉5〈/sub〉. The density functional theory is employed for determination of magnetic exchange constants, which are then used in Monte Carlo calculations. The symmetry analysis reveals that CaFeF〈sub〉5〈/sub〉 does not show magnetoelectric properties, whereas SrFeF〈sub〉5〈/sub〉 is a multiferroic.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Premkumar Murugaiyan, Amitava Mitra, Arun Kumar Patro, Rajat K. Roy, M. Churyukanova, S. Kaloshkin, E. Shuvaeva, Ashis K. Panda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The influence of P on amorphizing ability, as-quenched microstructure, thermo-physical and soft magnetic properties of Fe–rich (i) Fe〈sub〉81〈/sub〉B〈sub〉15-x〈/sub〉P〈sub〉x〈/sub〉Si〈sub〉2〈/sub〉Nb〈sub〉1〈/sub〉Cu〈sub〉1〈/sub〉 (ii) Fe〈sub〉82〈/sub〉B〈sub〉14-x〈/sub〉P〈sub〉x〈/sub〉Si〈sub〉2〈/sub〉Nb〈sub〉1〈/sub〉Cu〈sub〉1〈/sub〉 and (iii) Fe〈sub〉83〈/sub〉B〈sub〉13-x〈/sub〉P〈sub〉x〈/sub〉Si〈sub〉2〈/sub〉Nb〈sub〉1〈/sub〉Cu〈sub〉1〈/sub〉 (x = 0, 2, 4, 6, 8 at%) melt-spun alloys are investigated. The substitution of P improves amorphization of alloys and restricts the formation of hetero-amorphous microstructure for Fe 83 at% ribbons at around (x = 8). The improvement in short range ordering of P containing clusters with varying Fe content has been discussed within the framework of Cluster-Glue atom model and supported by experimental thermal parameters. The optimal P content in Fe-rich alloys in the range of 4 ≤ x ≤ 6 delivered favourable thermal properties of high primary and secondary crystallization onset temperature viz; T〈sub〉x1〈/sub〉, T〈sub〉x2〈/sub〉 and temperature span ΔT between these onsets. The P substitution drastically restricts the precipitation of secondary crystallites with reduced enthalpy of secondary crystallisation (ΔH〈sub〉2〈/sub〉) during annealing and favourably assists in attaining maximum magnetic moment during the primary crystallization stage. Moreover, the P substitution (4–8 at%) effects refinement of α-Fe nanocrystallites and promotes low coercivity (H〈sub〉c〈/sub〉 〈 20 A/m) in nanocomposite alloys. On contrary, the P substitution linearly reduces saturation magnetization (M〈sub〉s〈/sub〉) by weakening ferromagnetic exchange coupling and ferromagnetic dilution. An optimal content of 4 at% P offers favourable combination of low H〈sub〉c〈/sub〉 and High M〈sub〉s〈/sub〉 in both amorphous and nanocomposite state.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Jia Liu, Gui Yun Tian, Bin Gao, Kun Zeng, Yang Zheng, Jinzhong Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One challenge of stress measurement by using Magnetic Barkhausen noise (MBN) is to build correlation model between MBN and micro magnetic characterization of the material. In particular, it highly requires a quantitative evaluation for micro-macro magnetic properties characterizing under the stress impaction. In this study, a correlation model between domain wall (DW) motion and MBN under tensile stress is established and promoted. Optical flow (OF) traces motion of magnetic domain images, which can quantify the status of DW motion during magnetization process. When applied field is in stress direction, tensile stress aligns the magnetic domains parallel to the stress direction and makes coercive field decrease. This can make a phenomenon vary of DW motion as well as MBN signal. The average velocity of DW motion (OF value) is proportional to MBN signal under tensile stress. Root mean square (RMS) and mean value are extracted from both DW motion velocity (OF value) and MBN signal to quantitatively analyze the changes under tensile stress to quantify the correlation between micro and macro magnetic parameters. In addition, the correlation model between DW motion and MBN is quantitatively analyzed in different locations to evaluate the repeatability of the correlation, as well as the effect of microstructure on MBN and DW motion under the tensile stress. The correlation coefficient of RMS and mean value show the highly correlation between DW motion and MBN, which in turn sheds deep understanding the micro-macro property-physic mechanisms. The proposed work has potential for interpretation of the statistical properties of MBN under different tensile stress by studying DW motion, which can be further applied for enhancing accuracy on stress measurement.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Atasi Chakraborty, Indra Dasgupta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have carried out a detailed first principles electronic structure calculations for d〈sup〉4〈/sup〉 double perovskite iridates Ba〈sub〉2〈/sub〉ScIrO〈sub〉6〈/sub〉 and Sr〈sub〉2〈/sub〉ScIrO〈sub〉6〈/sub〉. Our calculations reveal that the ground state of both the systems to be magnetic contrary to the expectation of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si14.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉J〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉eff〈/mi〉〈/mrow〉〈/msub〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉0〈/mn〉〈/mrow〉〈/math〉 nonmagnetic state induced by strong spin-orbit coupling. Our exact diagonalization calculation with two site many body Hamiltonian suggests that hopping induced delocalization of holes leads to the formation of local moments in these systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Arnab Roy, P.S. Anil Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It is well known from theoretical models that a ferromagnetic system should undergo a disorder induced phase transition in its magnetization reversal mode at a critical disorder level 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si18.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉R〈/mi〉〈/mrow〉〈mrow〉〈mi〉C〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, below which, the reversal is characterized by the appearance of the so-called 〈em〉spanning avalanche〈/em〉. The 〈em〉critical〈/em〉 regime above 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si19.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉R〈/mi〉〈/mrow〉〈mrow〉〈mi〉C〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 is characterized by power-law distributed avalanche sizes and durations, whose exponents determine the universality class to which the magnetic system belongs. The most commonly studied among these is the size-exponent 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si20.svg"〉〈mrow〉〈mi〉τ〈/mi〉〈/mrow〉〈/math〉, which most theoretical models estimate to be in the range 1.3–1.5. However, experimental determinations of this exponent fall in a much wider interval, between 0.98 and 1.8, well outside the domain of the models. This discrepancy, which is far more common for 2D systems, has not been effectively addressed for more than a decade. In this article, we have determined experimentally the size-exponent ‘〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si21.svg"〉〈mrow〉〈mi〉τ〈/mi〉〈/mrow〉〈/math〉’ in 2D Permalloy(〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si22.svg"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉Ni〈/mtext〉〈/mrow〉〈mrow〉〈mn〉80〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si23.svg"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉Fe〈/mtext〉〈/mrow〉〈mrow〉〈mn〉20〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉) thin films by measuring Barkhausen noise through the disorder-induced transition using planar Hall effect. This was compared with our simulations of the random field Ising model, an established nucleation model, with a modification that better represented the experimental condition. Our findings indicated that 〈em〉large〈/em〉 ‘〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si24.svg"〉〈mrow〉〈mi〉τ〈/mi〉〈/mrow〉〈/math〉’-values would arise in samples with very low disorder levels well outside the critical regime, where the statistics were non-universal. In such samples, our measured ‘〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si25.svg"〉〈mrow〉〈mi〉τ〈/mi〉〈/mrow〉〈/math〉’ increased monotonically with temperature, which indicated a decrease in the effective disorder with temperature according to the nucleation models. This temperature dependence could be understood in the light of an 〈em〉extended〈/em〉 Néel-Brown model which we had studied earlier, that had predicted a decrease in the width of switching field distribution with increasing temperature. In this context, we also used micromagnetic simulations, which helped to understand the dependence of coercivity on disorder, a property not predicted correctly by the Ising model.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): L. Capogna, V. Granata, B. Ouladdiaf, J.A. Rodriguez-Velamazan, R. Fittipaldi, A. Vecchione〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have investigated the metamagnetic-like transition in the triple layer ruthenate Sr〈sub〉4〈/sub〉Ru〈sub〉3〈/sub〉O〈sub〉10〈/sub〉 by means of neutron diffraction from single crystals. The magnetic structure of the compound appears to be determined in a complex way by the two substructures of inequivalent ruthenium ions. At T〈sub〉c〈/sub〉=105K the system has a sharp transition into a ferromagnetic state along the 〈em〉c〈/em〉-axis which is driven by the ruthenium atoms in the central octahedra of the triple layers whereas the substructure of the outer ruthenium atoms tend to align in the 〈em〉ab〈/em〉 plane achieving an antiferromagnetic order at the metamagnetic transition T*∼50K. Below T* the strong anisotropy along 〈em〉c〈/em〉 prevails, the outer ruthenium tend to align along the 〈em〉c〈/em〉-axis and the in-plane antiferromagnetic order disappears. This finding confirms the delicate balance between antiferro and ferromagnetic couplings in the (Sr,Ca)〈em〉〈sub〉n〈/sub〉〈/em〉〈sub〉+1〈/sub〉Ru〈em〉〈sub〉n〈/sub〉〈/em〉O〈sub〉3〈/sub〉〈em〉〈sub〉n〈/sub〉〈/em〉〈sub〉+1〈/sub〉 family of compounds, and proves the layer dependence of the magnetic anisotropy in Sr〈sub〉4〈/sub〉Ru〈sub〉3〈/sub〉O〈sub〉10〈/sub〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): K.F. Ulbrich, C.E.M. Campos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocrystalline Nickel sulfide, Ni〈sub〉3〈/sub〉S〈sub〉2〈/sub〉, was prepared mechanochemically using ball milling in an inert atmosphere at room temperature, starting from Ni〈sub〉60〈/sub〉S〈sub〉40〈/sub〉 powder mixtures. X-ray powder diffraction (XRPD) was used to investigate the structural and microstructural evolution of the Ni〈sub〉60〈/sub〉S〈sub〉40〈/sub〉 alloy with milling time. The formation of the trigonal Ni〈sub〉3〈/sub〉S〈sub〉2〈/sub〉 phase (space group R32H) occurs with only 1.5 h, remaining stable up to 24 h of milling. The cell volume, lattice parameters, atomic coordinates, and isotropic atomic dislocation (thermal) parameters of the Ni〈sub〉3〈/sub〉S〈sub〉2〈/sub〉 phase, together with the average crystallite size and micro-strain, were determined from Rietveld analysis of the XRPD data. The average crystallite size decreases from about 37 nm to 22 nm with milling time increasing, with the same behavior happening for micro-strain. The high-temperature experiments showed that the melting point of the nanocrystalline Ni〈sub〉3〈/sub〉S〈sub〉2〈/sub〉 is about 660 °C, which is much lower than bulk. Transmission electron microscopy (TEM) images and electron diffraction patterns confirmed the nanometric size of the crystalline domains but revealed that it belongs to larger agglomerated particles (~100 nm). The nanocrystalline samples have their magnetic properties characterized by vibrating sample magnetometer (VSM), showing an evolution from ferromagnetism to a mixed magnetic state as milling time increases. The high-pressure experiments revealed no phase transitions up to 20 GPa and a bulk modulus of about 143 GPa for the Ni〈sub〉3〈/sub〉S〈sub〉2〈/sub〉 nanophase using the least-squares fit of first-order Murnaghan equation of states.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885319315240-ga1.jpg" width="268" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): S. Couture, X. Wang, A. Goncharov, V. Lomakin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A coupled micromagnetic-Maxwell equations solver is presented which takes into account the effect of eddy currents. The proposed solver relies on a strategy involving two parallel solvers, one for the micromagnetic equation, the other for the Maxwell equations, which allows o take advantage of the linearity of the Maxwell equations. Both the micromagnetic and Maxwell equations portions of the solver use a finite element formulation and they perform time integration in parallel with each other using a variable time stepping scheme. A finite element formulation for the Maxwell equations coupled with a micromagnetic solver is proposed. The resulting sparse linear system is solved using a preconditioned iterative method. Since the system matrix changes depending on the time step used, the preconditioner used is an ILU factorization which is interpolated from a set of pre-computed ILU factorizations, thus avoiding the need to recompute a factorization at every time step. The proposed solver is validated by solving a test problem with a known analytical solution. The performance of the solver is illustrated by solving a realistic hard-disk drive recording head model.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Wei Zhang, Zhaojun Mo, Wenhao Jiang, Zhihong Hao, Jiawei Luo, Ruijiang Cheng, Guodong Liu, Lan Li, Jun Shen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The EuTi〈sub〉1−x〈/sub〉Al〈sub〉x〈/sub〉O〈sub〉3〈/sub〉 (〈em〉x〈/em〉 = 0.05, 0.1 and 0.15) compounds exhibit the ferromagnetic state. A giant reversible MCE of EuTi〈sub〉1−x〈/sub〉Al〈sub〉x〈/sub〉O〈sub〉3〈/sub〉 (〈em〉x〈/em〉 = 0.05, 0.1, 0.15) compounds was observed, which was attributed to the increase of ferromagnetic ordering. With increasing the Al content, the value of −Δ〈em〉S〈sub〉M〈/sub〉〈sup〉max〈/sup〉〈/em〉 is increased from 11.6 J/kg K to15.6 J/kg K for EuTi〈sub〉1−x〈/sub〉Al〈sub〉x〈/sub〉O〈sub〉3〈/sub〉, and the RC values are 48.4 J/kg for EuTi〈sub〉0.95〈/sub〉Al〈sub〉0.05〈/sub〉O〈sub〉3〈/sub〉, 53.1 J/kg for EuTi〈sub〉0.9〈/sub〉Al〈sub〉0.1〈/sub〉O〈sub〉3〈/sub〉 and 58.2 J/kg for EuTi〈sub〉0.85〈/sub〉Al〈sub〉0.15〈/sub〉O〈sub〉3〈/sub〉 with magnetic field change 0–1 T. Additionally, the maximum value of Δ〈em〉T〈sub〉ad〈/sub〉〈/em〉 is 4.7 K for EuTi〈sub〉0.85〈/sub〉Al〈sub〉0.15〈/sub〉O〈sub〉3〈/sub〉 compound as magnetic field changes 1 T. The EuTi〈sub〉1−x〈/sub〉Al〈sub〉x〈/sub〉O〈sub〉3〈/sub〉 with giant −Δ〈em〉S〈sub〉M〈/sub〉〈/em〉, large RC and large ΔT〈em〉〈sub〉ad〈/sub〉〈/em〉 suggest an important material for magnetic refrigerant at low-temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Yudeuk Kim, David Juseong Bang, Yonghwan Kim, Jinyong Jung, Namjung Hur, Chun-Yeol You, Kyong Hon Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have measured the magneto-optic (MO) properties of film-type bismuth substituted yttrium iron garnets (Bi1.5:YIG, Bi〈sub〉1.5〈/sub〉Y〈sub〉1.5〈/sub〉Fe〈sub〉5〈/sub〉O〈sub〉12〈/sub〉) prepared by using metal-organic-decomposition (MOD) method on glass substrates at the 1310-nm and 1550-nm wavelengths. The Verdet constant of the Bi1.5:YIG film in the unsaturated linear magnetization region has been experimentally determined from a sensitive measurement of the Faraday rotation of the Bi1.5:YIG films with a lock-in amplifier and an auto-balanced photoreceiver under alternating magnetic fields. The Bi:YIG films have been deposited on silica glass substrates without any buffer layer and with one of buffer layers of Bi〈sub〉1〈/sub〉Y〈sub〉2〈/sub〉Fe〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 (Bi1:YIG) and Bi〈sub〉1〈/sub〉Fe〈sub〉4〈/sub〉Ga〈sub〉1〈/sub〉Nd〈sub〉2〈/sub〉O〈sub〉12〈/sub〉 (Bi1:NIGG) which are used to compensate mismatch of the lattice constant and thermal expansion coefficient between the film and substrate. The maximum value of the measured Faraday rotation of the Bi1.5:YIG film was over 94.6 and 156.5 °/cm for an applied unsaturated magnetic field of 100 Gauss at wavelengths of 1310 and 1550 nm, respectively, when it was prepared at annealing temperature of 700 °C and annealing speed of 1 °C/min. The absorption coefficients of the Bi1.5:YIG films were measured to be 70 cm〈sup〉−1〈/sup〉 and 330 cm〈sup〉−1〈/sup〉, respectively, at each of the wavelengths, and the average Gilbert damping coefficient of the Bi1.5:YIG film with a Bi1:NIGG buffer layer was measured to be 6.42 ± 18.09 × 10〈sup〉−4〈/sup〉 (with the minimum value of 0 and the maximum value of 24.51 × 10〈sup〉−4〈/sup〉) from a conventional ferromagnetic resonance (FMR) measurement system. Our experimental result indicates that the magneto-optic property of the Bi:YIG films prepared by the MOD method is unstable and fluctuates from run to run although its average magnetic property may be useful for application to compact integrated optical isolators under an easy solution-based fabrication process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): R.L. Souza, J.C.B. Monteiro, A.O. dos Santos, L.P. Cardoso, L.M. da Silva〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Here, we report the results of structural, magnetic, thermal and magnetocaloric properties of ErCoSn compound. The compound undergoes an antiferromagnetic (AFM) ordering around T〈sub〉N〈/sub〉 = 4.6 K and magnetic correlation is observed above T〈sub〉N,〈/sub〉 up to T = 11 K. Below T〈sub〉N〈/sub〉, a spin-glass state was observed for ErCoSn due to an apparent coexistence of ferromagnetic (FM) interaction with long-range AFM order. External applied magnetic field induces a first-order-like metamagnetic phase transition from AFM to FM state that is responsible for the large values of the maximum isothermal entropy change (−〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈msubsup〉〈mi mathvariant="normal"〉Δ〈/mi〉〈mrow〉〈mi〉M〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="italic"〉max〈/mi〉〈/mrow〉〈/msubsup〉〈/mrow〉〈/math〉 = 16.5 J/kgK@50 kOe) and adiabatic temperature change (ΔT〈sub〉ad〈/sub〉 = 8.2 K). Furthermore, short-range ferromagnetic correlation above T〈sub〉N〈/sub〉 contributes to the widening of −ΔS〈sub〉M〈/sub〉 and ΔT〈sub〉ad〈/sub〉 peaks as well as the increase of the ErCoSn compound refrigerant capacity. The results indicate attractive properties of this compound for magnetic refrigeration at cryogenic temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): C.E. Zaspel〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dynamic properties of magnetic vortices in single nanopillars, such as the gyrotropic orbital radius and frequency, have been shown to be well-modeled by the Thiele equation. Similarly, a set of coupled Thiele equations also describe synchronization of two or more interacting free layer vortices. Here the Thiele equations are used to model vortex dynamics in linear chains of alternating radius (where nearest-neighbor free layer have different radii) free layer oscillators, which is a system of interacting non-identical oscillators that can synchronize and lock onto a common frequency. For vortices interacting as magnetic dipoles it is shown that there are critical nanopillar separations below which the oscillator chain will synchronize. As the nanopillar separation increases, it is noticed that there is a narrow region of parameter space where synchronization is temporarily lost owing to phase slips and at larger separation synchronization is lost completely. The relation between the critical separation and the free layer radii difference is also estimated analytically.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Fei Huang, Wenxu Zhang, Bin Peng, Wanli Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a method to directly obtain the pure inverse spin Hall effect (ISHE) signal without the spin rectification effect (SRE) signal in ferromagnetic metal(FM)/nonmagnetic metal(NM) bilayers. This method is based on a fact that the distribution of the induced microwave current is largely dependent on the geometries of the samples. The ISHE signal can be maximized through shaping the samples and tuning the magnetic field directions, while the SRE signal can be minimized below the detection limit. This provides also a fast and simplified method to measure the ISHE signal in a wide frequency range. The spin Hall angle of Ta in a Py/Ta bilayer is −0.027 ± 0.015 in a wide frequency range.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Wu Liu, Weiping Zhang, Wenyuan Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The diamagnetically levitated electrostatic micromotor (DLEM), in which five degree of freedom of the levitated pyrolytic graphite rotor are stabilized by permanent magnets except its rotational degree of freedom around the main axis, was studied. The DLEMs were fabricated by using Micro-Electro-Mechanical Systems (MEMS) process and precision machining. The levitation properties of DLEM, which have been analyzed by the finite-element method (FEM) software Ansoft Maxwell 3D, were proved by the levitation experiments. Based on our designed measurement and control system, we successfully realized the continuous operation of the axial variable-capacitance motor by open-loop and closed-loop control. For DLEM1 device, under the fixed frequency and variable frequency open-loop logic with driving voltage of 43 V in air, the achieved rotational speed is 15.4 r/min and 70.0 r/min, respectively. For DLEM2 device, under the variable frequency open-loop and closed-loop control with driving voltage of 30 V in air, the achieved rotational speed is 46.9 r/min and 26.8 r/min, respectively. Experimental results show that the motor presents high reliability under the closed-loop rotational control.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Yan Liu, Xiaohong Huo, Shengjie Xuan, Huan Yan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic skyrmions are swirling nanometric spin textures, which have attracted extensive attention by virtue of their potential applications as information carriers for future memory technology and spintronic devices. Here, we investigate the effect of strain gradient on the in-plane current-driven motion of magnetic skyrmion in a nanotrack. It is found that a longitudinal strain gradient will induce a transverse velocity with its value linearly proportional to the strain gradient. As well, we find that skyrmions can be accelerated or decelerated by the boundary of nanotrack. This behavior depends on the repulsive force induced by boundary and the topological number of skyrmion. Our results not only explain the effect of strain gradient, but also show the influence of the boundary on the skyrmion motion. This work may provide a guide for designing and developing the racetrack memory based on magnetic skyrmions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Li Zhang, Yu Feng, Yilin Han, Tie Yang, Xiaotian Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Several 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉R〈/mi〉〈mover accent="true"〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈mrow〉〈mo stretchy="false"〉¯〈/mo〉〈/mrow〉〈/mover〉〈mi〉c〈/mi〉〈/mrow〉〈/math〉 Dirac half-metallic materials have been proposed and investigated based on first principles. A certain energy value in one spin channel with a clear band gap in the other spin channel leads to the half-metallic properties of these materials and multiple linear band dispersions (Dirac-like crossings) around the Fermi level for fast and low energy consumption electron transmission. In this work, a material synthesized in a prior experiment, PrNiO〈sub〉3〈/sub〉, was found to be a novel half-metallic material with multiple Dirac-like band dispersions according to the first principles. In this work, four magnetic states, i.e., ferromagnetic (FM), nonmagnetic (NM), and antiferromagnetic (AFM-1 and AFM-2) were considered in the 1 × 1 × 1 unit cell of PrNiO〈sub〉3〈/sub〉. Two cases of superlattices, 1 × 1 × 2 and 2 × 2 × 1, were built to study the most stable magnetic state of these systems. We found that the FM is the most stable magnetic state for the 1 × 1 × 1, 1 × 1 × 2, and 2 × 2 × 1 systems. The effects of uniform strain, hole and electron doping, and spin-orbit coupling on its electronic structures were discussed in detail. We hope this work can encourage more experimental and theoretical research on 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉R〈/mi〉〈mover accent="true"〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈mrow〉〈mo stretchy="false"〉¯〈/mo〉〈/mrow〉〈/mover〉〈mi〉c〈/mi〉〈/mrow〉〈/math〉-type half-metallic materials with multiple Dirac-like band dispersions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): W. Wang, X.C. Kan, X.S. Liu, C.C. Liu, K.M.U. Rehman, M. Shezad, Q.Y. Wu, S.Q. Zhou, Y.Y. Wang, Z. Wazir〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The critical behavior of the antiperovskite crystal Fe〈sub〉3.4〈/sub〉In〈sub〉0.6〈/sub〉N has been systematically studied in this paper. We have used a modified Arrott plot, the Kouvel-Fisher method, and critical isotherm analysis to obtain the critical exponents (〈em〉β〈/em〉, 〈em〉γ〈/em〉 and 〈em〉δ〈/em〉) which suggest that a long-range magnetic coupling described by mean-field (MF) theoretical model is dominant in Fe〈sub〉3.4〈/sub〉In〈sub〉0.6〈/sub〉N. The experimental 〈em〉M〈/em〉−〈em〉T〈/em〉−〈em〉H〈/em〉 relations below and above Curie temperature (〈em〉T〈/em〉〈sub〉c〈/sub〉) collapse into two branches by the single scaling equation 〈em〉m〈/em〉 = 〈em〉f〈/em〉〈sub〉±〈/sub〉(〈em〉h〈/em〉) (〈em〉m〈/em〉 and 〈em〉h〈/em〉 are renormalized magnetization and field), respectively. The critical exponents are confirmed by the Widom scaling law 〈em〉δ〈/em〉 = 1 + 〈em〉γβ〈/em〉〈sup〉−1〈/sup〉. In addition, it is suggested that the ferromagnetic (FM), anti-ferromagnetic (AFM) interactions and the magnetic disorders result to the exchange distance which is obtained just as 〈em〉J〈/em〉(〈em〉r〈/em〉)∝〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msup〉〈mrow〉〈mi〉r〈/mi〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉4.4〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Syed Ismail Ahmad, Abdul Rauf, Tasneem Mohammed, Amal Bahafi, D. Ravi Kumar, Madireddy Buchi Suresh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, we report frequency and temperature dependent dielectric, electrochemical impedance and low temperature magnetic properties of Sol-gel auto-combustion synthesized rare-earth (Ce and Sm) co-substituted cobalt ferrite, CoCe〈sub〉x〈/sub〉Sm〈sub〉y〈/sub〉Fe〈sub〉2-x-y〈/sub〉O〈sub〉4〈/sub〉 (x = y = 0.00, 0.1, 0.12 and 0.25). The surface morphology and particle size as obtained by XRD studies was confirmed by HRTEM measurements for a representative sample. The dielectric properties such as dielectric constant, loss tangent and AC conductivity have been measured using LCR meter, variation of dielectric parameters with substituent concentrations, frequency range from 0.1 to 10 MHz at room temperature (RT) and temperatures 100–400 °C have been well supported by Maxwell-Wagner interfacial polarization. The AC conductivity increased with applied frequency suggesting that the conduction mechanism is owing to small polaron hopping between cations. Impedance studies shows that, the addition of RE (Ce and Sm) cause a decrease in the Z′ value, with increasing frequency which can be attributed to the space charge polarization effect in the material. Low temperature magnetic measurements in ZFC-FC mode and magnetic isotherms at 20 and 310 K reveals the ferromagnetic nature of RE (Ce, Sm) substituted cobalt ferrite nano particles. The coercive field has been increased at low temperature 20 K compared to that at 310 K, the samples shows super paramagnetism beyond room temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Nasir Ali, Budhi Singh, Subhasis Ghosh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The room temperature ferromagnetism in doped and co-doped ZnO is reported here. X-ray photoelectron spectroscopy revealed the mixed oxidation states of Cu and Ag in ZnO:Cu and ZnO:Ag films, respectively. However, co-doping of Cu and Ag with Al does not alter their bonding characteristics in ZnO. Al in +3 oxidation state indicates that substitution of Al to Zn site gives an extra electron which increases the conductivity of ZnO:Ag and ZnO:Cu films. Mott variable range hopping dominates the conduction in ZnO:Cu and ZnO:Ag films whereas thermally activated conduction dominates in Al co-doped ZnO:Ag and ZnO:Cu films. We show that Ruderman–Kittel–Kasuya–Yosida mechanism is not responsible for ferromagnetism in Cu and Ag doped ZnO as the increase in carrier concentration due to Al co-doping does not enhance the ferromagnetism. Finally, possible mechanism behind the ferromagnetism is discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): V.К. Ignatiev, N.G. Lebedev, A.A. Orlov, S.V. Perchenko〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In a theoretical part of the paper a macroscopic model, based on quantum approaches, of a deformed magnetically soft ferromagnet is proposed for the α-iron crystal sample. The statistical transition to a multidomain sample is carried out and dynamical equations of the Bloch type are obtained. In the framework of modelling approximations and the Runge-Kutta numerical method, a solution of dynamic equations in the form of a complete hysteresis loop is obtained. The dependences of hysteresis loop parameters on the crystal tetragonallity and the relative deformation are studied. In an experimental part the magneto-elastic effect (the Villari effect) in the steel ER70S-6 sample is investigated. A comparison of model results with experimental data is shown a qualitative and quantitative agreement. Also a series of experiments are carried out to research magneto-plastic effects in the steel 9MnSi5 sample. It is found the effect of a mechanical erasure of a magnetic memory of a metal (MMM). An application of the theoretical model to research the obtained MMM effect is shown a quantitative agreement with experimental data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 491〈/p〉 〈p〉Author(s): Jānis Cīmurs, Artis Brasovs, Kaspars Ērglis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The stability of a paramagnetic prolate or oblate spheroidal particle in a precessing magnetic field is studied. The bifurcation diagram is calculated analytically as a function of the magnetic field frequency and the precession angle. The orientation of the particle in the synchronous regime is calculated. The rotational dynamics and the mean rotational frequency in the asynchronous regime are also obtained. The theoretical model we describe enables the analytic calculation of the dynamics of the particle in the limiting case when the motion is periodic. The theoretical models were also compared with experimental results of rod like particle dynamics in a precessing magnetic field. The experimental results are in good agreement with the proposed theory.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Kirill V. Sobolev, Kamil K. Kolincio, Andrey Emelyanov, Aleksandra Mielewczyk-Gryń, Maria Gazda, Marta Roman, Anna Pazniak, Valeria Rodionova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Herein we initiate a comeback to the arc melting technique to produce MAX-phase solid solutions. Bulk samples of (Cr〈sub〉1−x〈/sub〉Mn〈sub〉x〈/sub〉)〈sub〉2〈/sub〉AlC MAX-phase with 〈em〉X〈/em〉 = 0, 0.025, 0.05 and 0.1 were synthesized and studied by means of X-ray diffractometry, scanning electron microscopy in combination with energy-dispersive X-ray spectroscopy. Samples were established to be homogeneous with an incorporation of Cr〈sub〉7〈/sub〉C〈sub〉3〈/sub〉, AlCr〈sub〉2〈/sub〉 and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 secondary phases which is slightly increasing with the raise of the dopant concentration. Manganese successfully intermixes in the MAX-phase structure due to the effect of the high-energetic plasma during the melting process. SQUID magnetometry identified the co-existence of ferro- and antiferromagnetic interactions with the latter prevailing in high temperatures and being attributed to the MAX-phase. Magnetic state transitions were observed at approximately 4 K and 5 K for doped samples which was associated with the presence of the marginal amount of ferromagnetic Mn-based secondary phases. The negative component of magnetoresistance was observed in highly doped samples at low temperatures that is likely due to the influence of ferromagnetic secondary phases as well. Transport properties measurement revealed the satisfactory quality of the produced samples.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Yu Feng, Zhou Cui, Xin Ruan, Xiaoyi Fu, Zhenxiang Cheng, R. Khenata, Xiaotian Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic tunnel junction (MTJ) device employing inverse Heusler alloy as electrode has great potential for application in spintronics. In this work, we performed first-principles calculations combined with nonequilibrium Green’s function to study the spin transport properties of Heusler alloy based Ti〈sub〉2〈/sub〉CoGe/MgO/Ti〈sub〉2〈/sub〉CoGe MTJ with various atomic terminations. The calculated interface free energy (〈em〉γ〈/em〉) indicates that TiCo-terminated interface could be easily formed than TiGe-terminated interface, and the interface containing pure Ge atom is the most favorable owing to its lowest 〈em〉γ〈/em〉. Spin transport calculations reveal that tunnel magnetoresistance (TMR) ratio in MTJ with natural TiCo terminated interface (1.58 × 10〈sup〉4〈/sup〉) is higher than that with natural TiGe-terminated interface (2.99 × 10〈sup〉3〈/sup〉). When the interfacial Ti atom in TiCo-terminated interface is substituted by Co atom, the transport ability of majority spin electrons is promoted. Moreover, our calculation indicates that the MTJ with the interface containing pure Co atom possesses the largest TMR ratio of 9.51 × 10〈sup〉5〈/sup〉. Our work paves the way for the fabrication of Ti〈sub〉2〈/sub〉CoGe based MTJ for practical application in spintronics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Chengrui Fu, Xingfan Zhang, Yunrui Duan, Xinyue Dai, Tao Li, Yujie Xia, Yanyan Jiang, Hui Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetism of Fe-Ni system is calculated from the first-principles. Results show that the atomic magnetic moments are determined by their local surrounding atoms. In both FM and AFM cases, the Fe atomic magnetic moment declines with increasing number of Fe atoms in its local surroundings. The relation between atomic volume and atomic magnetic moment indicates that Fe-rich local surroundings would cause relatively small volumes. Our work is of significance to understanding the relation between the local surroundings with anomalous thermal expansion coefficient in the Invar alloy.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Li Zhang, Yilin Han, Houari Khachai, R. Khenata, Xiaotian Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This current investigation builds upon previous results (Ma et al., 2018), which have shown that LaMnO〈sub〉3〈/sub〉 is a novel Dirac half metal with multiple Dirac-like cones. In this work, a new 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉R〈/mi〉〈mover accent="true"〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈mrow〉〈mo stretchy="false"〉¯〈/mo〉〈/mrow〉〈/mover〉〈mi〉c〈/mi〉〈/mrow〉〈/math〉 phase material, TbNiO〈sub〉3〈/sub〉, with 100% spin-polarization and robust multiple Dirac-cones has been focused on. By means of first-principles and quasi-harmonic Debye model, its electronic, magnetic and thermodynamic properties have been studied, and also, the effects of uniform strain and on-site Coulomb interaction U on its electronic structures have been discussed. Moreover, the magnetic states, including FM, NM, and AFM, were fully considered in a 1 × 1 × 1 unit cell and two superlattice cells, i.e., 1 × 1 × 2 and 2 × 2 × 1 systems. We hope this work will trigger further research about 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉R〈/mi〉〈mover accent="true"〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈mrow〉〈mo stretchy="false"〉¯〈/mo〉〈/mrow〉〈/mover〉〈mi〉c〈/mi〉〈/mrow〉〈/math〉 type Dirac half-metallic materials with multiple Dirac cones in experimental and theoretical regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): E.M. Kutashova, A.V. Pyataev, N.F. Shkodich, A.S. Rogachev, Yu.B. Scheck〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The process of phase formation during short-term (80 and 120 min) high-energy ball milling of Fe〈sub〉84〈/sub〉B〈sub〉16〈/sub〉, Fe〈sub〉80〈/sub〉B〈sub〉20〈/sub〉, and Fe〈sub〉70〈/sub〉B〈sub〉30〈/sub〉 powder mixtures was studied by Mössbauer spectroscopy. Hyperfine field 〈em〉B〈/em〉〈sub〉hf〈/sub〉 on the nuclei of resonant atoms as a function of the number of boron atoms (〈em〉n〈/em〉〈sub〉B〈/sub〉) in the nearest neighborhood of Fe atoms was also found to be a linear function of 〈em〉n〈/em〉〈sub〉B〈/sub〉 and for 〈em〉n〈/em〉〈sub〉B〈/sub〉 = 5–11: 〈em〉B〈/em〉〈sub〉hf〈/sub〉 = 33.7 – 2.7〈em〉n〈/em〉〈sub〉B〈/sub〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Bingyang Meng, Jiexin Hou, Fengzhi Ning, Bai Yang, Bohui Zhou, Ronghai Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have provided a new and simple coating strategy to fabricate high-performance metal-based magnetic composites exhibiting both high magnetic inductions and decreased core loss. High-purity submicron FeCo particles have been dispersed into silicone resin to form a magnetic insulating film, which is then coated uniformly on the particle surface of high-purity Fe powders with a particle size of 170 μm to form new-type Fe-based soft magnetic composites (SMCs). These insulated magnetic layers containing submicron FeCo particles in these Fe-based SMCs can maintain very high saturated magnetization (209 A·m〈sup〉2〈/sup〉·kg〈sup〉−1〈/sup〉) for the composites, and also result in their low core loss. For traditional metal-based SMCs, the low core loss is often obtained accompanying with seriously decreased magnetic inductions. In present work, both high magnetic inductions and decreased core loss in company with high compacted density are achieved in these Fe-based SMCs coated with magnetic insulating coating layers. Specifically, the extremely low eddy current loss occurring in these new Fe-based SMCs enables their latent applications in low-loss and high-power magnetic devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): V.A. Milyutin, I.V. Gervasyeva〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents new investigations of high magnetic field (HMF) effects on phase and structural transformations as well as historical development of the problem. The regularities of structure evolution under simultaneous action of heat treatment and high magnetic field have been studied on different alloys. It was shown, that magnetic field can affect thermodynamics and kinetics of transformation, which results in changes in the phase composition, crystallographic texture, rate of transformation, morphology of precipitating particles, and other effects. The observed phenomena strongly depend on magnetic properties of phases involved into transformation such as magnetic moment, magnetic susceptibility, magneto-crystalline anisotropy, magnetostriction. The review comprises the main results of modern researches into the influence of magnetic field of tens Tesla on the phase and structural transformations in materials with different type of magnetic ordering. Further research directions of HMF effect on the thermally activated transformations are proposed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): Muhammad Arshad, M. Asghar, Muhammad Junaid, Muhammad Farooq Warsi, M. Naveed Rasheed, M. Hashim, M.A. Al-Maghrabi, Muhammad Azhar Khan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study Co-Ni co-doped nanocrystalline manganese ferrites were fabricated via co-precipitation method. The annealing of as prepared nanoferrites was done at 950 °C for 7 h. The powder X-ray diffraction (XRD) confirmed that all samples possessed cubic spinel structure. The crystallite size was determined by Scherrer’s equation that lies in the range of 27–35 nm. The spectral analysis confirmed bending and stretching of bonds at octahedral (B) and tetrahedral (A) sites. The spectral bands were shifted towards the longer wavelength side and these indicate the incorporation of dopants cations (Co-Ni). The magnetic parameters were measured from the M-H loops of nanoferrites. With the increase of Co-Ni contents, the saturation magnetization (Ms) increased up to x = 0.15 and then it decreased. The dielectric properties of all compositions were studied in 1 MHz–3 GHz range and were discussed in the light of Debye-type reduction phenomenon by following the Koop’s theory. The dielectric and magnetic behavior evaluation suggested that synthesized ferrites are suitable for microwave devices fabrication.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318319127-ga1.jpg" width="282" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): Dongyan Zhang, Zhimin Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ferromagnetic MPB in the Tb〈sub〉x〈/sub〉Dy〈sub〉1−x〈/sub〉Co〈sub〉2〈/sub〉 system was confirmed via both experimental and theoretical research, which demonstrates the simultaneous structural change with ferromagnetic phase transition. According to the ferromagnetic MPB theory, a phenomenological thermodynamic model of Tb〈sub〉x〈/sub〉Dy〈sub〉1−x〈/sub〉Co〈sub〉2〈/sub〉 at Dy-rich side was constructed. The thermodynamic model predicts the behavior of DyCo〈sub〉2〈/sub〉, which is consistent with the experimental value. The phenomenological thermodynamic model based on ferromagnetic MPB could be employed to make a quantitative analysis of magnetostrictive or magnetocaloric materials.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): F.M. Abbasi, I. Shanakhat, S.A. Shehzad〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Entropy generation analysis for peristalsis of nanofluid with temperature dependent viscosity has been carried out. Mathematical formulation is executed using “long wavelength” approximation. Hall effects and Ohmic heating are also included. Arising non-linear equations are solved using Homotopy Perturbation Method. Analytical solutions for temperature, axial velocity, Bejan number and entropy generation are obtained and examined through graphs. Results show that for enhanced values of nanoparticles volume fraction both velocity and temperature decreases. Increasing values of viscosity parameter decreases the temperature. Moreover, entropy generation and Bejan numbers show decreasing behaviors for increase in nanoparticles volume fraction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Bang-Qing Li, Yu-Lan Ma, Perumal Sathishkumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A coupled nonlinear system is investigated, which describes the nonlinear short-wave propagation in nanoscale saturated ferromagnetic materials. A series of analytic solutions is constructed via Riccati equation mapping method. Furthermore, two types of novel periodically oscillating solitons are observed by choosing the arbitrary function in the soliton solution as trigonometric function and Jacobian elliptic function, respectively. The parameters can be used to control the compression, stretch, oscillating amplitude and frequency of the solitons.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 475〈/p〉 〈p〉Author(s): X.J. Weng, L.C. Shen, H. Tang, G.P. Zhao, J. Xia, F.J. Morvan, J. Zou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coercivity mechanism has been studied intensively and debated for many years in magnetic materials, particularly in permanent magnets where defects play important roles in adjusting the coercivity. Such a role can be manifested in hard/soft multilayers, where the soft layer can be taken as an enlarged soft defect, which normally exists in so-called single-phased permanent magnets. In this paper, hysteresis loops and spin distributions have been obtained based on both three-dimensional (3D) and one-dimensional (1D) micromagnetic methods for SmCo/Fe to reveal the in-depth coercivity mechanism. Two different geometric models have been constructed to mimic the experimental trilayers, in one of which a transition layer between hard and soft layers is adopted, where calculated nucleation fields and coercivity match very well with the experimental data. As the soft layer thickness increases, both nucleation and coercive fields reduce whilst the coercivity mechanism changes from nucleation to pinning. Such a pinning is inherently related to nucleation and has both attributes of traditional nucleation and pinning, called as a hybrid coercivity mechanism here. The thickness-dependent coercivity mechanism obtained in this work agrees perfectly with the experimental data, which is general for all hard/soft composites and can be extended to single-phased permanent magnets where defects are inevitable.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): P.T.T. Le, Mohsen Yarmohammadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We study the magnon-charged impurity interaction effects on the magnonic heat capacity (MHC) and the Pauli magnetic susceptibility (PMS) of spin-1/2 and spin-3/2 Lieb lattice within the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si18.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉J〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈/mrow〉〈/msub〉〈mo〉-〈/mo〉〈msub〉〈mrow〉〈mi〉J〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 Heisenberg model in the presence of the Dzyaloshinskii-Moriya interaction (DMI) and the Zeeman magnetic field. In so doing, we use the Green’s function technique and the full self-consistent Born approximation. We found that in the case of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si19.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉J〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 Heisenberg model, the MHC and PMS increase (decrease) with impurity concentration for spin-1/2 (spin-3/2), while oscillate (decrease) when coupling constants next-nearest-neighbor (NNN), DMI, and the Zeeman field are taken into account. We have also investigated perturbed MHC and PMS by ascertained impurity for different coupling strengths, resulting in the oscillating (decreasing) behavior with NNN for spin-1/2 (spin-3/2) and a decreasing behavior with DMI and Zeeman magnetic field for both spin-1/2 and spin-3/2. Moreover, magnetic phase transitions in the case of spin-3/2 are established when tuning coupling constants on the non-zero, whilst no magnetic phase transition is observed for spin-1/2 Lieb lattice. Our findings are useful to tune the physical properties of optical lattices subjected to the electric field, magnetic field, and charged impurity.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 475〈/p〉 〈p〉Author(s): Petr Ostroverkhov, Alevtina Semkina, Aleksey Nikitin, Alexander Smirnov, Daria Vedenyapina, Kseniya Vlasova, Igor Kireev, Mikhail Grin, Vladimir Chekhonin, Alexander Majouga, Maxim Abakumov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic nanoparticles are widely used in various fields of biomedicine. They can combine both therapy and diagnostics modalities thus opening many opportunities for their application. In our work, we have evaluated their ability to work as contrast agents for magnetic resonance imagining and drug delivery systems for photosensitizers. We have shown that after formation of human serum albumin retains ability to bind photosensitizers and they do not lose their optical properties. To obtain stable water solution suitable for long term storage we have additionally modified human serum albumin with polyethylene glycol. It was shown that such modification allows to increase overall stability over time.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): S. Vorobiov, D. Tomasova, V. Girman, H. You, E. Čižmár, M. Orendáč, V. Komanicky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Structural parameters of nanomagnet arrays have been systematically adjusted in order to study and to maximize the magnetocaloric effect. Optimum technological parameters were experimentally established and arrays of nanomagnets based on Ni〈sub〉3〈/sub〉Pt nanoparticles with a different structure period (1, 2, 3 μm) and two different heights (1.2 and 1.9 μm) were fabricated using electron-beam lithography followed by electrodeposition. The obtained arrays have a phase composition of fcc-Ni〈sub〉3〈/sub〉Pt, which remains unchanged after annealing. It was shown that a change in the period of the nanomagnet arrays leads to a change in the magnitude of the magnetocaloric effect and the operating temperature range. Also, changes in the height of nanomagnets from 1.2 to 1.9 μm lead to an increase in the magnetocaloric response by more than 30%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): T.J. Hicks, T. Keller, A.R. Wildes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Neutron resonant spin echo spectroscopy has been applied to measure the splitting of the magnon bands due to the magnetic dipole interaction in the two dimensional antiferromagnet MnPS〈sub〉3〈/sub〉. The splittings measured are more than two orders of magnitude smaller than energies of the magnons. Simulation of the magnon energies involving the calculation of the magnetic dipole interaction in MnPS〈sub〉3〈/sub〉 predict splittings a little higher than those measured. The comparison confirms that the magnetic dipole interaction provides most of the anisotropy which stabilises the antiferromagnetic order in MnPS〈sub〉3.〈/sub〉 We present the first evidence for the splitting of magnon bands due to the magnetic dipole interaction in a two dimensional antiferromagnet.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): A.H. Gevorgyan, S.S. Golik, T.A. Gevorgyan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The peculiarities of transmission and angular non-reciprocity in magneto-photonic crystals (MPC) are investigated. The problem of light transmission through magneto-photonic crystal is solved by Ambartsumian’s modified layer addition method. It is shown that the system under consideration can work as a wide band ideal optical diode for orthogonal circular polarizations and as a narrow band ideal optical diode for orthogonal linear polarizations. The influence of the magnitude of external static magnetic field, its direction, and the angle of incidence on the diode properties are investigated.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Takuya Shiga, Daisuke Ishikawa, Minami Tachibana, Ryo Saiki, Graham N. Newton, Hiroki Oshio〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A tetranuclear iron grid-type spin crossover complex, [Fe〈sup〉II〈/sup〉〈sub〉4〈/sub〉(HL)〈sub〉4〈/sub〉](BF〈sub〉4〈/sub〉)〈sub〉4〈/sub〉•6H〈sub〉2〈/sub〉O (〈strong〉1〈/strong〉) (H〈sub〉2〈/sub〉L = 2-(4-hydroxyphenyl)-4,5-bis{6-(3,5-dimethylpyrazol-1-yl)pyrid-2- yl}-1〈em〉H〈/em〉-imidazole), was synthesized. Magnetic susceptibility measurements revealed that 〈strong〉1〈/strong〉 shows gradual spin crossover behavior above 200 K. The electronic states of the compound were elucidated by Mössbauer spectra.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉A tetranuclear iron grid-type spin crossover complex, [Fe〈sup〉II〈/sup〉〈sub〉4〈/sub〉(HL)〈sub〉4〈/sub〉](BF〈sub〉4〈/sub〉)〈sub〉4〈/sub〉•6H〈sub〉2〈/sub〉O (〈strong〉1〈/strong〉) (H〈sub〉2〈/sub〉L = 2-(4-hydroxyphenyl)-4,5-bis{6-(3,5-dimethylpyrazol-1-yl)pyrid-2-yl}-1〈em〉H〈/em〉-imidazole), was synthesized. Magnetic susceptibility measurements revealed that 〈strong〉1〈/strong〉 showed gradual spin crossover behavior above 200 K. The electronic states were elucidated by Mössbauer spectra.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318335790-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): A. Dashora, J. Sahariya, H.S. Mund, M.D. Mukadam, S.M. Yusuf, M. Itou, Y. Sakurai, G. Arora, B.L. Ahuja〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The role of excess Ni in Ni〈sub〉2+x〈/sub〉Mn〈sub〉1-x〈/sub〉Sn (x = 0.05, 0.1) Heusler alloys has been reported using temperature dependent magnetic Compton spectroscopy. The experimental Compton profiles from magnetic electrons have been analyzed to quantify the contribution of Mn 3d electrons, Ni sites and sp-electrons in building-up the total spin moments. The experimentally deduced spin momentum densities, total and element-specific spin moments are examined using theoretical investigations within the spin polarized relativistic Korringa-Kohn-Rostoker method. The build-up of spin moments has been explored in terms of total and projected density of states. Site-dependent Ni magnetic moment is also discussed. Heisenberg exchange coupling parameters are also computed to study the change in Ruderman-Kittel-Kasuya-Yosida type exchange interaction on increasing Ni concentration in the Ni-Mn-Sn system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): C. Papusoi, T. Le, P-O. Jubert, D. Oswald, B. Ozdol, D. Tripathy, P. Dorsey, M. Desai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of a 1.5 nm thick CoX layer (CAP) of high Curie temperature 〈em〉T〈sub〉C〈/sub〉〈/em〉, deposited on top of an L1〈sub〉0〈/sub〉 Fe〈sub〉50〈/sub〉Pt〈sub〉50〈/sub〉 layer (MAG) on the properties of the MAG/CAP bilayer is investigated. Two series of samples are studied: “w/o CAP” are single MAG layers of thickness in the 3.8–10.5 nm range and “w/ CAP” are MAG/CAP bilayers of MAG thickness in the 3.8–10.5 nm range and 1.5 nm CAP. For both series, magnetization reversal is investigated at 〈em〉T〈sub〉RT〈/sub〉〈/em〉 = 300 K and is shown to be coherent rotations up to a MAG thickness threshold of 〈em〉t〈sub〉cr〈/sub〉〈/em〉 ∼ 7.5 nm and incoherent, domain-wall mediated, above 〈em〉t〈sub〉cr〈/sub〉〈/em〉. The dependence of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.gif" overflow="scroll"〉〈msub〉〈mfenced open="|" close="|"〉〈mrow〉〈mi〉d〈/mi〉〈msub〉〈mi〉H〈/mi〉〈mrow〉〈mi mathvariant="italic"〉RC〈/mi〉〈/mrow〉〈/msub〉〈mo stretchy="false"〉/〈/mo〉〈mi〉d〈/mi〉〈mi〉T〈/mi〉〈/mrow〉〈/mfenced〉〈mrow〉〈mi〉T〈/mi〉〈mo〉=〈/mo〉〈msub〉〈mi〉T〈/mi〉〈mi〉C〈/mi〉〈/msub〉〈/mrow〉〈/msub〉〈/math〉, where 〈em〉H〈sub〉RC〈/sub〉〈/em〉 is the remanence coercivity, on the MAG thickness indicates 〈em〉t〈sub〉cr〈/sub〉〈/em〉 is poorly dependent on temperature from 〈em〉T〈sub〉RT〈/sub〉〈/em〉 up to the MAG 〈em〉T〈sub〉C〈/sub〉〈/em〉. The MAG 〈em〉T〈sub〉C〈/sub〉〈/em〉 distribution, of average 〈〈em〉T〈sub〉C〈/sub〉〈/em〉〉 and standard deviation 〈em〉σ〈sub〉TC〈/sub〉〈/em〉, is evaluated for both series. The results indicate 〈〈em〉T〈sub〉C〈/sub〉〈/em〉〉 is higher and 〈em〉σ〈sub〉TC〈/sub〉〈/em〉/〈〈em〉T〈sub〉C〈/sub〉〈/em〉〉 is lower w/ CAP than w/o, particularly at low MAG thicknesses. This behavior is interpreted as a consequence of spin exchange hardening in the MAG layer in the proximity of the MAG/CAP interface. For the w/ CAP case, the saturation field of the Thermoremanent magnetization exhibits a non-motononic dependence on the MAG thickness, displaying a maximum. This behavior indicates the CAP assists the applied field to set the MAG layer magnetization during a HAMR process, the assist effect becoming more efficient the lower is the MAG thickness.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 483〈/p〉 〈p〉Author(s): Lei Xie, Anding Wang, Shiqiang Yue, Aina He, Chuntao Chang, Qiang Li, Xinmin Wang, Chain-Tsuan Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fe-based soft-magnetic amorphous and nanocrystalline ribbons made with a single-side fast-cooling process always suffer from the surface crystallization which deteriorates the magnetic properties and inhibits the wide applications. In this study, a static magnetic field assisted melt-spinning process was employed to prepare the typical Fe〈sub〉84.75〈/sub〉Si〈sub〉2〈/sub〉B〈sub〉9〈/sub〉P〈sub〉3〈/sub〉C〈sub〉0.5〈/sub〉Cu〈sub〉0.75〈/sub〉 alloy ribbon with an attractive application prospect. According to the comparative investigations of the crystallization behavior, structural evolution process and magnetic properties, it is found that the applied magnetic field can effectively inhibit the formation of compound phases and decrease the size of textured 〈em〉α〈/em〉-Fe grains in the surface layer of the as-spun ribbon. The Fe〈sub〉84.75〈/sub〉Si〈sub〉2〈/sub〉B〈sub〉9〈/sub〉P〈sub〉3〈/sub〉C〈sub〉0.5〈/sub〉Cu〈sub〉0.75〈/sub〉 samples made with low purity raw materials and under an optimal field exhibit superior magnetic properties, including a high saturation magnetization (〈em〉B〈/em〉〈sub〉s〈/sub〉) over 1.82 T, low coercivity (〈em〉H〈/em〉〈sub〉c〈/sub〉) of 8.5 A/m, high permeability (〈em〉μ〈/em〉) of 2.76 × 10〈sup〉4〈/sup〉 at 1 kHz and much lower losses, after nanocrystallization by annealing. The apparent effect of the applied magnetic field was discussed from the disturbance of a Lorentz force of the fast-moving molten alloy and a magnetic force of preformed grains in a magnetic field during the melt-spinning process. These results provide a novel solution of surface crystallization and an effective route for improving magnetic properties of Fe-based amorphous and nanocrystalline alloy ribbons.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 26 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Shuang Zhao, Yuye Wu, Jingmin Wang, Yuxiao Jia, Tianli Zhang, Tianle Zhang, Chengbao Jiang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Acquisition of large coercivity remains as a key issue in MnAl permanent-magnet alloys. In this work, we successfully introduce rhombohedral nanoprecipitates with the size of ∼20 nm into L1〈sub〉0〈/sub〉 MnAl alloys via doping 0.2 at.% Tb and melt spinning technology. The motion of magnetic domain walls can be more effectively pinned by the dispersive nanoprecipitates. This results in an improved coercivity of 5.43 kOe in Tb-0.2 at.% powders which is 22% larger than that of the binary powder without significant degrading in saturation magnetization and magnetocrystalline anisotropy. This work may provide a new method to improve the coercivity in MnAl permanent magnets.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318338988-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 26 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Alexander Omelyanchik, Gaspare Varvaro, Mikhail Gorshenkov, Anatoly Medvedev, Alexey Bagazeev, Igor Beketov, Rodionova Valeria〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic and structural properties of metallic α-Fe magnetic nanoparticles synthesized by electric explosion of wire technique were investigated. As-prepared particles are highly crystalline and present a high saturation magnetization (M〈sub〉S〈/sub〉 = 186±3 emu/g) that is slightly lower than bulk value (M〈sub〉α-Fe〈/sub〉 = 218 emu/g) due to the presence of a very thin non-magnetic FeO〈sub〉x〈/sub〉 shell, which increases the chemical stability and biocompatibility, making the particles of great interest for a number of applications, including sensing and biomedicine. When the particles are pressed, strong dipole-dipole interactions arise, giving rise to collective ferromagnetic-like behavior observed with magnetic force microscopy, which results in a reduction of the coercivity, thus suggesting that the interparticle interactions can be used as an additional tool to tune the magnetic properties.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Satoshi Akamaru, Akihiro Kimura, Masanori Hara, Katsuhiko Nishimura, Takayuki Abe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic properties of Pd–Co alloys and their hydrides were investigated. From the temperature dependences of magnetization of Pd–Co alloys, simple ferromagnetic behaviors were observed, and the Curie temperatures are estimated to be 220, 315, and 350 K for Pd〈sub〉0.96〈/sub〉Co〈sub〉0.04〈/sub〉, Pd〈sub〉0.92〈/sub〉Co〈sub〉0.08〈/sub〉, and Pd〈sub〉0.90〈/sub〉Co〈sub〉0.10〈/sub〉, respectively. The Pd–Co alloys were hydrogenated under 100 kPa hydrogen gas pressure. After hydrogenation, the temperature variations of magnetization revealed two magnetic transitions implying that there are two phases in the hydrogenated Pd–Co: the hydrogen dissolution and hydride phases. The hydrogen contents ([H]/[Pd–Co]) and the Curie temperature (〈em〉T〈/em〉〈sub〉C〈/sub〉) of the hydride phase are deduced that [H]/[Pd–Co] = 0.53, 0.43 and 0.36 with 〈em〉T〈/em〉〈sub〉C〈/sub〉 = ≤50, 100 and 120 K for Pd〈sub〉0.96〈/sub〉Co〈sub〉0.04〈/sub〉, Pd〈sub〉0.92〈/sub〉Co〈sub〉0.08〈/sub〉, and Pd〈sub〉0.90〈/sub〉Co〈sub〉0.10〈/sub〉 hydrides, respectively. The magnetization against externally applied field measured at 50 and 300 K indicated that the magnetic moments per a single ion (Pd, Co) of the hydrides are always smaller than those of the original Pd–Co alloys. First principle calculations for the magnetic moments provided quite consistent results with the experimental ones.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): O.M. Sousa, J.S. Lima, A.F. Lima, M.V. Lalic〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A thorough theoretical study of the spinel Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 compound subjected to pressures from 0 to 30 GPa has been performed by using density functional theory and by probing different exchange-correlation (XC) potentials to depict the experimental facts. It is found that GGA-PBE XC functional correctly describes the structural properties of the antiferromagnetic normal-spinel phase at P=0, while the Becke-Johnson XC potential correctly describes its electronic structure and the gap of 0.76 – 0.82 eV, reported in the most recent experimental studies. It is concluded that the inverse-spinel phase does not form within the investigated pressure range. Instead, it is found that the Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 exhibits a phase transition at the pressure of 10.7 GPa, maintaining its global crystal structure but exhibiting different local structural characteristics (Co-O bond lengths, oxygen positions) and changing its electronic and magnetic properties. At this pressure, the band gap exhibits a sudden drop and the magnetic moment of the tetrahedral Co completely disappears, so the compound undergoes a phase transition from normal-spinel antiferromagnetic phase to spinel non-magnetic phase. While electronic and magnetic properties of the Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 under pressure were not investigated experimentally yet, its pressure dependent structural properties agree well with the most recent experimental study.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Philip Kern, Christoph Döpke, Tomasz Blachowicz, Pawel Steblinski, Andrea Ehrmann〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanostructured ferromagnetic materials are applicable in a broad range of technologies, especially in the areas of data storage and spintronics. In addition, special structures are of high interest in basic research, aiming at understanding magnetization reversal processes on the nano-scale and thus possibly creating new applications. The strong influence of the shape anisotropy in magnetic nanoparticles enables tailoring magnetization reversal processes by the shape of such a particle. Typically, symmetrical structures are investigated, such as nano-dots, doughnuts, squares, rectangles, etc. Here we report on spiral nano-structures with constantly varying bending radii, modelled according to the Fibonacci spiral which is well-known from diverse plants and biological processes and also related to many mathematical problems. The magnetic Fibonacci nano-spirals with a thicker and a thinner lateral structure size as well as a mirrored form, building a heart-like shape, show large numbers of steps in the hysteresis loops, corresponding to stable intermediate states, due to nucleation and annihilation of domains which do not propagate along the spirals. The numbers of these stable intermediate states which could be utilized for data storage as well as the coercive fields depend strongly on the spiral dimensions and the orientation of the external magnetic field. Simulating minor loops showed the high stability of the intermediate states and thus underlined the possibility to use such structures for data storage.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Kun Yu, Kai Liu, Shengcan Ma, Xingqi Han, Zhishuo Zhang, Ying Song, Yuxi Zhang, Changcai Chen, Xiaohua Luo, Zhenchen Zhong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, Ni-Co-Mn-Ti ferromagnetic shape memory alloy thin films, which consists of all 3〈em〉d〈/em〉 metals, are well prepared by direct-current (DC) double targets magnetron co-sputtering method. The deposition temperature (DT) dependence of microstructure and magnetic properties is studied in these thin films. The elemental compositions of these thin films are almost invariable, while the average grain size increases with the increasing DT. Micro-morphology shows that the crystal grains of films are spherical and homogeneous. For the samples deposited at 523 K and 573 K, an unusual magnetization reversal behavior is observed at ∼342 K and ∼225 K, respectively, in the thermomagnetic curves at the applied field 〈em〉μ〈/em〉〈sub〉0〈/sub〉〈em〉H〈/em〉=1 T. Meanwhile, the hysteresis loops at ambient temperature demonstrate that in Ni-Co-Mn-Ti thin films the ferromagnetic contribution increases at the expense of diamagnetic one as DT increases. The reasons for these results are discussed.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318337053-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 29 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): G.C. DeFotis, J.C Molloy, C.H. Komatsu, M.J. Van Dongen, C.M. Davis, C.L. DeSanto, W.M. May, T.M. Owens〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Effects of disorder, frustration and low dimensional character occur in mixed magnetic Co〈sub〉1-x〈/sub〉Ni〈sub〉x〈/sub〉Cl〈sub〉2〈/sub〉∙H〈sub〉2〈/sub〉O, examined by dc magnetization and susceptibility measurements across the composition range. The pure components are quasi-one-dimensional antiferromagnets ordering at 15.0 K (Co) and 5.6〈sub〉5〈/sub〉 K (Ni), with susceptibility maxima at 16.2 and 8.4 K respectively; a spin glass transition also appears in the cobalt system near 8 K. In each compound weaker antiferromagnetic interchain exchange interactions supplement dominant ferromagnetic exchange along MCl〈sub〉2〈/sub〉MCl〈sub〉2〈/sub〉M… chemical and structural chains. High temperature magnetic susceptibilities are analyzed to yield Curie and Weiss constants in χ〈sub〉M〈/sub〉 = C/(T-θ). Regular but not mean-field composition dependences appear for C and θ. The former is not linear and the latter displays a minimum near x = 0.30. Notable is a susceptibility maxima varying in location only weakly from x = 0.10 to x = 0.70, decreasing markedly only for higher x. Magnetization isotherms evolve regularly as x varies, with systematic composition dependences of a metamagnetic transition field and hysteresis through x = 0.70. A qualitative change in the isotherms occurs for x = 0.90, but substantial curvature still appears with smaller but definite hysteresis. A thermoremanent magnetization is seen in all mixtures, and is largest for the composition extremes. Thus, nonequilibrium magnetic behavior characteristic of the cobalt component, in contrast to the more conventional nickel component, occurs even when the latter is present in strong majority.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Merve Zuvin, Muhammed Koçak, Özlem Ünal, Yunus Akkoç, Özlem Kutlu, Havva Yağci Acar, Devrim Gözüaçik, Ali Koşar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic hyperthermia has received much attention during the last decade due to its implementation in cancer treatment. Recently, functionalized superparamagnetic iron oxide nanoparticles (SPION) emerged as a strong alternative adjuvant treatment approach, which complements conventional methods such as chemotherapy. In this study, we demonstrate the anticancer effect of Poly(acrylic acid)-coated, anti-HER2-tagged SPIONs on breast cancer cells using a low magnetic field strength of 0.8 kAm〈sup〉-1〈/sup〉, which is significantly lower compared to the literature, with a frequency of 400 kHz. Specificity was achieved via anti-HER2 antibody attachment to nanoparticles. HER2-positive SKBR3 and MDA-MB-453 cell lines internalized the nanoparticles successfully. These nanoparticles, which were not toxic to these cell lines, led to a prominent decrease in cell proliferation and survival in MDA-MB-453 cells when subjected to hyperthermia. Therefore, the hyperthermia-targeted SPION approach could be developed as a potential cancer treatment approach against breast cancer and possible other cancer types.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Biswanath Bhoi, N. Venkataramani, Shiva Prasad, R.P.R.C. Aiyar, Gulshan Kumar, I. Samajdar, M. Kostylev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic properties and FMR of pulsed laser deposited Y〈sub〉3〈/sub〉Fe〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 (YIG) thin film on Gd〈sub〉3〈/sub〉Ga〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 (111) substrate have been investigated in the temperature range 4.2 ≤ 〈em〉T〈/em〉 ≤ 〈em〉300 K〈/em〉. The effective saturation magnetization (4πM〈sub〉eff〈/sub〉), obtained from Ferromagnetic Resonance at room temperature, is found to be 2600 G, which is higher than SQUID measured 4πM〈sub〉S〈/sub〉 value of 1770 G. This implies that the value of 4πM〈sub〉eff〈/sub〉 can only be accounted by considering a negative anisotropy field (H〈sub〉U〈/sub〉) of around 830 Oe at room temperature. Such an anisotropy is attributed to a compressive stress (-1.70 ×10〈sup〉10〈/sup〉 dyne/cm〈sup〉2〈/sup〉) induced in the film closer to the film-air interface. The presence of this stress in YIG film was confirmed using multiple {〈em〉hkl〈/em〉} stress measurements with grazing incidence X-ray diffraction performed at different depth of penetration on the YIG film.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Mario A. Castro, Álvaro P. Espejo, Nicolas M. Vargas, Dora Altbir, Sebastian Allende, Vagson L. Carvalho-Santos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic energy of nanorings with variable anisotropy along their radius have been studied using analytical calculations and micromagnetic simulations. Based on the ge- ometric characteristics of nanorings, four magnetic states are considered, looking to the relatively lower energy magnetization configuration as a function of anisotropy and geometry. Analytical phase diagrams with these states are presented showing that changes in the anisotropy yield the appearance of new magnetic states, here called meron and knot-like states, appear. Nevertheless, micromagnetic simulations evidence that the knot-like state can be interpreted as a vortex configuration with a magnetization that rotates around the border of the ring. The possibility of obtaining new magnetic states is interesting as from fundamental as from applied viewpoint.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Stanislav Kunikin, Arthur Zakinyan, Yuri Dikansky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The experimental study of the dynamic magnetic susceptibility of the powder of superparamagnetic nanoparticles of magnetite is presented. The powder has been obtained by removal (evaporation) of the liquid base of the magnetic colloidal solution (ferrofluid). The temperature dependences of the real and imaginary parts of the magnetic susceptibility at different frequencies of the measuring field have been obtained. The experimental findings are compared with the results of the simulations based on the numerical solution of the Landau-Lifshitz-Gilbert equation for the interacting superparamagnetic nanoparticles system. The conclusion has been made on the significant influence of the interparticle interactions on the magnetite superparamagnetic nanoparticles powder properties evidenced, in particular, by the decreased effective system relaxation time.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Bommareddy Poojitha, Anjali Rathore, Surajit Saha〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Materials having strong coupling between different degrees of freedom such as spin, lattice, orbital, and charge are of immense interest due to their potential device applications. Here, we have stabilized the 9R phase of BaMnO〈sub〉3〈/sub〉, by Sr (Ti) doping in the Ba (Mn) site using solid-state route at ambient pressure, which otherwise requires high-pressure conditions to synthesize. Crystal structure, phonon spectra, and their evolution with temperature are investigated using x-ray diffraction and Raman spectroscopic techniques. Temperature-dependent magnetization data reveal an antiferromagnetic transition at around (T〈sub〉N〈/sub〉 =) 262 K and 200 K for Ba〈sub〉0.9〈/sub〉Sr〈sub〉0.1〈/sub〉MnO〈sub〉3〈/sub〉 and BaMn〈sub〉0.9〈/sub〉Ti〈sub〉0.1〈/sub〉O〈sub〉3〈/sub〉, respectively. No structural phase transition or lattice instabilities are observed in the measured temperature range (80 – 400 K) for both the compounds. We have observed anomalous behaviour of four different phonon modes involving Mn/O-vibrations at low temperatures which have been attributed to spin-phonon coupling.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Temperature-dependent Raman spectroscopy is used to investigate the phonons in the 9R-Ba〈sub〉0.9〈/sub〉Sr〈sub〉0.1〈/sub〉MnO〈sub〉3〈/sub〉 (BSM10) and BaMn〈sub〉0.9〈/sub〉Ti〈sub〉0.1〈/sub〉O〈sub〉3〈/sub〉 (BMT10). An Mn vibration with E〈sub〉g〈/sub〉 symmetry near 344 cm〈sup〉-1〈/sup〉 shows anomalous behaviour with temperature below ∼ 262 K and ∼ 200 K for BSM10 and BMT10, respectively. Three additional vibrations involving Mn/O atoms also show phonon anomalies. Magnetic measurements suggest an antiferromagnetic ordering below these temperatures while x-ray diffraction data suggest no lattice deformation or structural phase transition. Therefore, phonon anomalies have been attributed to originate from spin-phonon coupling. Using mean field approximation, the spin phonon coupling strength for the 〈em〉E〈/em〉〈sub〉g〈/sub〉 mode is estimated to be 3.2 cm〈sup〉-1〈/sup〉.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318341015-ga1.jpg" width="448" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 483〈/p〉 〈p〉Author(s): Hongjian Li, Qiong Wu, Ming Yue, Yuqing Li, Yitong Zhuge, Dajun Wang, Jiuxing Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In present study, surfactant assisted ball-milling method was applied to prepare SmCo〈sub〉5〈/sub〉 nanoflakes, which were then magnetically aligned and warm compacted with a liquid binder to make bulk anisotropic SmCo〈sub〉5〈/sub〉 bonded magnets. Warm compaction with magnetic-field-assisted liquid phase processing can decrease the viscosity of the binder to enhance the alignment of the magnetic nanoflakes, and thus can produce high density magnets, providing a novel method to fabricate anisotropic bonded magnets. The magnetic properties, microstructure, and crystal alignment of both nanoflakes and bonded magnets are systematically investigated. The X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM) characterizations suggest that the obtained liquid phase bonded magnets exhibit enhanced magnetic anisotropy compared with those without magnetic field alignment and the solid phase bonded anisotropic magnets. The remanence of anisotropic phenol formaldehyde (PF) bonded magnets (4.43 kG) is higher than isotropic bonded magnets (3.76 kG), and the energy product of bonded magnets increases from 3.4 MGOe to 4.8 MGOe under the effect of the magnetic field.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Jun He, Lianwen Deng, Heng Luo, Longhui He, Dongyong Shan, Shuoqing Yan, Shengxiang Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ti〈sub〉3〈/sub〉SiC〈sub〉2〈/sub〉 particles encapsulated by Ni〈sub〉0.5〈/sub〉Zn〈sub〉0.5〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 shell were in-situ synthesized via a facile sol-gel method. Effects of Ni〈sub〉0.5〈/sub〉Zn〈sub〉0.5〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 shell on electromagnetic properties of Ti〈sub〉3〈/sub〉SiC〈sub〉2〈/sub〉 were investigated in 2–18 GHz. Moderated complex permittivity and desirable higher complex permeability presented for the Ni〈sub〉0.5〈/sub〉Zn〈sub〉0.5〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/Ti〈sub〉3〈/sub〉SiC〈sub〉2〈/sub〉 composite, resulting in strong microwave attenuation ability and good impedance matching property. The measured effective absorbing bandwidth (RL 〈 −10 dB) of 5.3 GHz and corresponding maximum RL of −38.6 dB were obtained for the Ni〈sub〉0.5〈/sub〉Zn〈sub〉0.5〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/Ti〈sub〉3〈/sub〉SiC〈sub〉2〈/sub〉 absorbing coating of 1.2 mm thickness. These results indicate that the Ni〈sub〉0.5〈/sub〉Zn〈sub〉0.5〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/Ti〈sub〉3〈/sub〉SiC〈sub〉2〈/sub〉 composite may become a new type of microwave absorbent.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Weikai Lei, Qingzheng Jiang, Sajjad Ur Rehman, Lunke He, Xianjun Hu, Qingwen Zeng, Qiulan Tan, Renhui Liu, Minglong Zhong, Zhenchen Zhong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The expensive rare earth elements Nd, Pr, Dy and Tb have been extensively used for making NdFeB-based magnets, but the less expensive and high abundant rare earth (HARE) elements such as La and Ce have been over stocked. The marketing expansion of the HARE elements is of much interest in academia and industry to achieve effective and efficient utilization of HARE elements. In this paper, nanocrystalline (Nd〈sub〉1−〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉La〈em〉〈sub〉x〈/sub〉〈/em〉)〈sub〉13〈/sub〉Fe〈sub〉81〈/sub〉B〈sub〉6〈/sub〉 (〈em〉x〈/em〉 = 0–0.5) alloys were fabricated by melt-spinning method. It is found out that the room temperature magnetic properties of the alloys decrease sharply when La is substituted for Nd up to 20 at.%. However, an anomalous increase in 〈em〉J〈/em〉〈sub〉r〈/sub〉 value and improved thermal stability of the alloy ribbons are observed for 40 at.% La substituted alloy while the reduction in magnetic properties is only nominal up to 30 at.%. Furthermore, the Curie temperature decreases from 588 K to 561 K with 50 at.% La substitution, which is higher than the equal amount of Ce substitution in Nd-Fe-B. It is shown by the Henkel curves that the alloy with 40 at.% La has the biggest value of positive peak which demonstrates the strongest exchange coupling in the 40 at.% La substituted alloy. The TEM micrographs indicate that the alloy containing 40 at.% La has more uniform and refined microstructure resulted in the enhanced properties.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 472〈/p〉 〈p〉Author(s): A.R. Moura, R.J.C. Lopes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We used the Self-Consistent Harmonic Approximation (SCHA) to study the thermodynamics of the precession magnetization in a two-dimensional isotropic ferromagnet. The SCHA treats the Hamiltonian in terms of the canonically conjugate operators 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si10.gif" overflow="scroll"〉〈mrow〉〈msup〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈mrow〉〈mi〉z〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si11.gif" overflow="scroll"〉〈mrow〉〈mi〉φ〈/mi〉〈/mrow〉〈/math〉 (the azimuth angle) including renormalized temperature dependent parameters to take into account higher order interactions. It is well-known that in right conditions, a dynamic magnetic field is able to provide spin pumping and drives the system to a magnon Bose-Einstein condensation. The magnon condensate is a coherent state that presents minimal uncertainty for the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si10.gif" overflow="scroll"〉〈mrow〉〈msup〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈mrow〉〈mi〉z〈/mi〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si11.gif" overflow="scroll"〉〈mrow〉〈mi〉φ〈/mi〉〈/mrow〉〈/math〉 operators. Consequently, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si14.gif" overflow="scroll"〉〈mrow〉〈mo stretchy="true"〉〈〈/mo〉〈msup〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈mrow〉〈mi〉z〈/mi〉〈/mrow〉〈/msup〉〈mo stretchy="true"〉〉〈/mo〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si15.gif" overflow="scroll"〉〈mrow〉〈mo stretchy="true"〉〈〈/mo〉〈mi〉φ〈/mi〉〈mo stretchy="true"〉〉〈/mo〉〈/mrow〉〈/math〉 should constitute natural fields to describe the model, which justifies the SCHA formalism. The results obtained are consistent with other theoretical and experimental works.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): T. Bartoli, K. Zehani, J. Moscovici, A. Michalowicz, L. Bessais〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocrystalline 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si115.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉PrCo〈/mtext〉〈/mrow〉〈mrow〉〈mn〉3〈/mn〉〈mo〉-〈/mo〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mtext〉Fe〈/mtext〉〈/mrow〉〈mrow〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈mo stretchy="false"〉(〈/mo〉〈mi〉x〈/mi〉〈mo〉⩽〈/mo〉〈mn〉1〈/mn〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈/math〉 powder samples were synthesized by high energy milling and subsequent annealing at 1023 K for 30 min. The samples crystallize in the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉PuNi〈/mtext〉〈/mrow〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉-type structure (space group 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈mrow〉〈mi〉R〈/mi〉〈mover accent="true"〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈mrow〉〈mo〉¯〈/mo〉〈/mrow〉〈/mover〉〈mi〉m〈/mi〉〈/mrow〉〈/math〉) for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si118.gif" overflow="scroll"〉〈mrow〉〈mi〉x〈/mi〉〈mo〉〈〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/math〉, confirmed by means of X-ray diffraction. In order to explain the original magnetic properties of these compounds and for the determination of the exchange interaction in theoretical models, the Fe and Co sites and occupancies in the crystallographic structures are required. However, standard XRD can not be used to determine Fe substitution sites, because Co and Fe have too close X-ray atomic scattering factors. Results from neutron diffraction and electronic band structure calculations from our previous works were incomplete or limited. Consequently, we give in this study the characterization of the local structure by X-ray absorption spectroscopy (EXAFS) at the iron K edge. By this method, and if we assume a unique preferential site, it was determined that Fe atoms preferably occupy the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si15.gif" overflow="scroll"〉〈mrow〉〈mn〉18〈/mn〉〈mi〉h〈/mi〉〈/mrow〉〈/math〉 site. In order to obtain this result, a coordination sphere around Fe sites of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si120.gif" overflow="scroll"〉〈mrow〉〈mi〉R〈/mi〉〈mo〉=〈/mo〉〈mn〉5.2〈/mn〉〈/mrow〉〈/math〉 Åhad to be considered in order to find sufficient local differences between the possible sites (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si15.gif" overflow="scroll"〉〈mrow〉〈mn〉18〈/mn〉〈mi〉h〈/mi〉〈/mrow〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si14.gif" overflow="scroll"〉〈mrow〉〈mn〉6〈/mn〉〈mi〉c〈/mi〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si53.gif" overflow="scroll"〉〈mrow〉〈mn〉3〈/mn〉〈mi〉b〈/mi〉〈/mrow〉〈/math〉). Furthermore, we provide complementary magnetic properties measurements for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉PrCo〈/mtext〉〈/mrow〉〈mrow〉〈mn〉3〈/mn〉〈mo〉-〈/mo〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mtext〉Fe〈/mtext〉〈/mrow〉〈mrow〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si125.gif" overflow="scroll"〉〈mrow〉〈mi〉x〈/mi〉〈mo〉⩽〈/mo〉〈mn〉0.75〈/mn〉〈/mrow〉〈/math〉) such as the coercive field 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si106.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉H〈/mtext〉〈/mrow〉〈mrow〉〈mi〉C〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, which decreases with iron content from 12 kOe for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si127.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉PrCo〈/mtext〉〈/mrow〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 to 1.5 kOe for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si128.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉PrCo〈/mtext〉〈/mrow〉〈mrow〉〈mn〉2.25〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mtext〉Fe〈/mtext〉〈/mrow〉〈mrow〉〈mn〉0.75〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉. The magnetization at saturation 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si17.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉M〈/mtext〉〈/mrow〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 increases from 69 A m〈sup〉2〈/sup〉/kg to 89 A m〈sup〉2〈/sup〉/kg and the calculated anisotropy field 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si18.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉H〈/mtext〉〈/mrow〉〈mrow〉〈mi〉a〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 decreases from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si131.gif" overflow="scroll"〉〈mrow〉〈mn〉15.6〈/mn〉〈/mrow〉〈/math〉 kOe to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si132.gif" overflow="scroll"〉〈mrow〉〈mn〉11.2〈/mn〉〈/mrow〉〈/math〉 kOe for the same compositions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Oznur Karaagac, Hakan Köçkar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, Taguchi method, response surface methodology and regression analyses have been applied to assess the effects of synthesis parameters on saturation magnetisation, M〈sub〉s〈/sub〉 of iron nanoparticles produced by hydrogen reduction of iron oxide nanoparticles. The M〈sub〉s〈/sub〉 values were obtained from the magnetisation loops measured by a vibrating sample magnetometer. Structural characterisations of the selected samples were done by X-ray diffraction technique and transmission electron microscopy. Orthogonal array L9 with three parameters (temperature, reaction time and H〈sub〉2〈/sub〉 flow rate) at three levels (low, medium and high) was used to obtain the experimental trials. Based on the signal to noise (S/N) ratio considering the condition larger is the better approach and the mean response, the highest M〈sub〉s〈/sub〉 condition has been found when the temperature is 800 °C m/min, reaction time is 60 min and H〈sub〉2〈/sub〉 flow rate is 1000 ml/min. Analysis of Variance (ANOVA) is applied to find out the F-ratio and percentage contribution of each parameter by using experimental trials and S/N ratios. It was found that the temperature was the most significant parameter on the M〈sub〉s〈/sub〉 of iron nanoparticles. A confirmation experiment has been carried out by using the experimental conditions obtained from Taguchi method. The M〈sub〉s〈/sub〉 of the optimum sample was found to be 217.42 emu/g which was within 95% confidence level with the predicted optimal M〈sub〉s〈/sub〉 of 214.03 emu/g. The quality losses for M〈sub〉s〈/sub〉 obtained at the highest combinations were 70.7%. In addition, analyses of multiple linear and quadratic regressions were employed to derive the predictive equations of the M〈sub〉s〈/sub〉 achieved via experimental design. The predicted values from the developed models and experimental values are found to be very close to each other justifying the significance of the models. Besides, the quadratic interactive regression model provided the best statistical performance with high R〈sup〉2〈/sup〉 and R〈sup〉2〈/sup〉(adj) values of 100 and 100%, respectively between the experimental and predicted values of M〈sub〉s〈/sub〉. More intensive predicted values were obtained by the quadratic regression models as compared to the multiple linear regression models. Taguchi prediction method was also very successful in the optimization of synthesis parameters for the highest M〈sub〉s〈/sub〉 of nanoparticles within the prescribed limit.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): L. Balejčíková, V.I. Petrenko, M. Baťková, K. Šipošová, V.M. Garamus, L.A. Bulavin, M.V. Avdeev, L. Almásy, P. Kopčanský〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Presence of protein amyloid aggregates is associated with many neurodegenerative disorders, such as Alzheimer’s disease etc. The effect of magnetoferritin and reconstructed ferritin on the structure of lysozyme amyloid aggregates was studied using small-angle X-ray scattering, atomic force microscopy and thioflavin T fluorescence measurements. It has been shown that both magnetoferritin and reconstructed ferritin molecules affect the size, structure and amount of the amyloid fibrils. We assume that the anti-amyloid effect of magnetoferritin and reconstructed ferritin is due to the presence of iron in solutions but is not associated with the magnetic character of the iron oxide phases, i.e. magnetite/maghemite for magnetoferritin and ferrihydrite for ferritin.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Philipp Lemal, Sandor Balog, Christoph Geers, Patricia Taladriz-Blanco, Andrea Palumbo, Ann M. Hirt, Barbara Rothen-Rutishauser, Alke Petri-Fink〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic hyperthermia for cancer treatment has gained significant attention in recent years, due to its biocompatibility of applied nanoparticles and the possibility for spatially localized heating in deep tissues. Clinical treatments use nanoparticle concentrations of 112 mg Fe/mL, while the concentrations experimental studies have addressed are considerably smaller, usually between 0.1 and 30 mg/mL. Therefore, it is not clear whether such experiments correspond to the magnetic properties found in clinical applications. In this regard, we studied the thermal behavior of superparamagnetic iron oxide nanoparticles (SPION) with the most common particle shapes used in the field, including spherical (core diameters 11 and 19 nm), cubic (15 nm) and ellipsoidal (23 nm with an aspect ratio of 1.45), at concentrations ranging from 5 to 80 mg Fe/mL. Their shape, size, crystallinity, magnetic, and thermal behavior were characterized via transmission electron microscopy, dynamic light scattering, Taylor dispersion analysis, X-ray diffraction, alternating gradient magnetometry, and lock-in thermography. Spherical and cubic nanoparticles displayed linear heating slopes, independent from size, shape and concentration, resulting in unchanged specific absorption rates (SAR). Ellipsoids showed the same behavior until 50 mg/mL, above which a decreasing heating slope trend was found, without evidence as to what causes this behavior. However, the presented results highlight the importance of colloidally stable SPIONs in magnetic hyperthermia to obtain maximum heating power by minimum particle dosage.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Peerasak Chantngarm, Bumned Soodchomshom〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We study pressure control of transport properties in graphene-based FM/B/FM junction where FMs are ferromagnetic graphene regions and B is graphene/MoS〈sub〉2〈/sub〉 heterostructure barrier. In graphene/MoS〈sub〉2〈/sub〉 heterostructure region, the Fermi energy has been found to be linearly pressure-dependent. Therefore, it is possible to control the currents by pressure in the presented structure. In non-magnetic junction, it was found that, the charge current depends almost linearly on pressure near the Dirac point. We find that the Dirac point can be shifted by varying back gate potential. The correlation between current and pressure in the junction may lead to applications for pressure sensors and pressure transistors. In magnetic junction, we predicted that the switching of spin polarization may occur at a specific pressure and spin current may be linearly controlled by pressure near the Dirac point. The results reveal the potentials of graphene/MoS〈sub〉2〈/sub〉 heterostructure for applications in pressure-controlled charge current and spin current devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Oznur Karaagac, Busra Bilir Yildiz, Hakan Köçkar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, superparamagnetic cobalt ferrite nanoparticles (SCFNs) were synthesized by co-precipitation in one-step. The synthesis parameters; reaction time and stirring rate, were varied separately while the other parameters were fixed constant to investigate the effect of the parameters on the properties of SCFNs. X-ray diffraction analysis and Fourier transform infrared spectroscopy confirmed that synthesized samples are cobalt ferrite. The magnetization consistently increased with the particle size as the reaction time increased and the stirring rate decreased. While the reaction time was effective on the size of the cobalt ferrite nanoparticles, the stirring rate was also found to have influence on the particle size and thus the magnetization of the nanoparticles. The critical size of cobalt ferrite nanoparticles for superparamagnetic limit with zero coercivity and remanence was found to be around 7 nm and its maximum magnetization value was 41.0 emu/g. When the size of the SCFNs went over 7 nm, the magnetization increased with a small coercivity of 2–5 Oe, which may offer a potential usage in magnetic hyperthermia applications. It was seen that structural properties, especially the particle sizes and corresponding magnetic properties of SCFNs were considerably affected by the parameters of stirring rate and especially reaction time. Therefore, it is seen that SCFNs with desirable properties can be tailored by changing the synthesis parameters and therefore may have the potential to use in biomedical applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Marina Mühlberger, Christina Janko, Harald Unterweger, Eveline Schreiber, Julia Band, Christian Lehmann, Diana Dudziak, Geoffrey Lee, Christoph Alexiou, Rainer Tietze〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉According to the World Health Organization, cancer is the second most important cause of death in Europe. Due to its manifold manifestations, it is not possible to treat all patients according to a uniform scheme. However, all solid tumors have one thing in common: independent of the tumor’s molecular subgroup and the treatment protocol, the immune status of the tumor, especially the amount of tumor infiltrating lymphocytes (TILs), is important for the patient’s clinical outcome – the higher the number of TILs, the better the outcome. For this reason it seems desirable to increase the number of TILs.〈/p〉 〈p〉One way to accumulate T cells in the tumor area is to make them magnetizable and attract them with an external magnetic field. Magnetization can be achieved by superparamagnetic iron oxide nanoparticles (SPIONs) which can be bound to the cells’ surface or internalized into the cells.〈/p〉 〈p〉For this study, SPIONs with different coatings were synthesized and incubated with immortalized mouse T lymphocytes. SPIONs only stabilized with lauric acid (LA) coated 〈em〉in situ〈/em〉 or afterwards showed high toxicity. Addition of an albumin layer increased the biocompatibility but reduced cellular uptake. To increase the cellular uptake the albumin coated particles were aminated, leading to both higher uptake and toxicity, dependent on the degree of amination. In the presence of an externally applied magnetic field, T cells loaded with selected types and amounts of SPIONs were guidable.〈/p〉 〈p〉With this promising pilot study we already can demonstrate that it is possible to attract SPION bearing T cells by an external magnet.〈/p〉 〈p〉To sum up, biocompatibility and uptake of SPIONs by T cells are opposing events. Thus, for the functionalization of T cells with SPIONs the balance between uptake and toxicity must be evaluated carefully.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 30 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Azhar Ali Zafar, Nehad Ali Shah, Ilyas Khan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, two-phase flow of blood is considered through a circular tube along with magnetic properties. The tube is considered as a circular cylinder form and the blood is flowing through it under the influence of uniform magnetic field and an external oscillating pressure gradient. Exact solutions for the fluid and magnetic particles velocities are obtained by means of integral transforms. The velocity of the fluid is presented as a sum of post transient and transient solutions. Moreover, a semi-analytical solution based on the Bessel equation and Tzou’s algorithm for the inverse Laplace transform is obtained. A comparison among the profiles of the fluid’s velocity determined with both solutions is also made. Furthermore, in order to study the influence of the material parameters, numerical simulations and graphical illustrations are used and useful conclusions are summarized.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): I.R. Souza Filho, M.J.R. Sandim, R. Cohen, L.C.C.M. Nagamine, H.R.Z. Sandim, D. Raabe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Strain-induced martensite (SIM) formation was evaluated upon cold-rolling of a 17.6 wt.%Mn-TRIP steel by means of magnetic measurements, X-ray diffraction, and high-resolution electron backscatter diffraction (EBSD). α′-martensite formation was observed to be dependent on the presence of prior ε-martensite. Upon deformation, the coercivity of the ferromagnetic α′-martensite is characterized by strong magnetic shape anisotropy. Austenite (γ) reversion was evaluated by means of in situ magnetic measurements during continuous annealing. The experimental results were compared to thermodynamic simulations. It turned out that γ-reversion was not completed in the regime where a γ-single phase field is expected, which suggests the splitting of α′ → γ transformation into two stages. The Curie temperature of remaining α′-martensite was determined as being ∼620 °C. Magnetic properties presented an annealing time-dependence within the temperature range of 500–600 °C, suggesting long-range diffusional α′ → γ transformation. With the aid of electron channeling contrast image technique (ECCI), we noticed that the formation of γ-nanograins in the early stages of reversion is sufficient to induce strong magnetic shape anisotropy in this steel. After full austenitization at 800 °C, further 〈em〉in〈/em〉 situ magnetic measurements were also used to track the magnetic response of the material upon controlled cooling. Athermal formation of α′-martensite within the prior athermal ε-phase was clearly observed for temperatures lower than 100 °C. Using thermodynamic modeling we also calculated the start temperature for ε-formation (〈em〉M〈sub〉s〈/sub〉〈/em〉〈sup〉ε〈/sup〉). Results showed that ε-martensite is indeed expected to form before α′, which was confirmed in all cases by means of EBSD.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318318948-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 472〈/p〉 〈p〉Author(s): D. Kostopoulos, I. Panagiotopoulos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Finite element micromagnetics are used to simulate remanence, hysteresis and dynamic switching in crescent shaped permalloy caps, a geometry that corresponds to either normal or oblique deposition of films on nanosphere arrays. Oblique deposition breaks the symmetry and favours onion states rather than vortices. It introduces in-plane shape anisotropy analogous to that of an elongated island and increases the in-plane coercivity. In isolated caps, the critical diameter above which the vortex state is the minimum energy state, is 〈em〉D〈/em〉 = 123 nm for angles below θ = 20 deg. It increases with θ up to a vlaue of 〈em〉D〈/em〉 = 157 nm at θ = 45 deg. Even for sizes for which the onion state is the lowest energy state, vortex states can be stabilized in isolated caps but the interparticle magnetostatic interactions tend to destabilize them driving the system to its ground state. The switching field of onion states can be reduced by 36% using microwave resonance at frequencies approaching the resonant (Kittel mode) frequencies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Gaurav Vats, Ravikant, Shalini Kumari, Dhiren K. Pradhan, Ram S. Katiyar, V.N. Ojha, Chris R. Bowen, Ashok Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study reports the magnetocaloric effect (MCE) and piezoresponse of integrated ferroelectric-ferromagnetic heterostructures of PbZr〈sub〉0.52〈/sub〉Ti〈sub〉0.48〈/sub〉O〈sub〉3〈/sub〉 (PZT) (5 nm)/Bi-Sr-Ca-Cu〈sub〉2〈/sub〉-O〈sub〉X〈/sub〉 (BSCCO) (5 nm)/La〈sub〉0.67〈/sub〉Sr〈sub〉0.33〈/sub〉MnO〈sub〉3〈/sub〉 (LSMO) (40 nm)/MgO (0 0 1). Magnetic and pizoresponse behavior of the heterostructures are found to be governed by magneto-electric coupling and induced lattice strains. In addition, a maximum MCE is studied using Maxwell equations from both Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization data. Maximum MCE entropy change (|Δ〈em〉S〈/em〉|) of 42.6 mJkg〈sup〉−1〈/sup〉K〈sup〉−1〈/sup〉 (at 258 K) and 41.7 mJkg〈sup〉−1〈/sup〉K〈sup〉−1〈/sup〉 (at 269 K) are found corresponding to FC and ZFC data, respectively. The variation in maximum entropy change and corresponding temperatures for FC and ZFC data revealed that the application of a magnetic field can significantly contribute towards tuning of the MCE. Interestingly, these multilayered structures are found to sustain MCE over a broad temperature range, which makes them attractive for improved solid-state energy conversion devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Anna C. Bakenecker, Anselm von Gladiss, Thomas Friedrich, Ulrich Heinen, Heinrich Lehr, Kerstin Lüdtke-Buzug, Thorsten M. Buzug〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The untethered actuation of milli- and microdevices is of great interest for a variety of medical applications. A millimeter sized swimmer is shown, which is 3D-printed and coated with magnetic nanoparticles. The coating has to fulfill two requirements: First, it must have a high magnetic moment in order to show a strong reaction to a magnetic field for good actuation performance. Second, it has to be suitable for magnetic particle imaging (MPI). MPI is an emerging medical imaging technique, based on the nonlinear response of superparamagnetic nanoparticles to oscillating magnetic fields. It is aimed at dual use of an MPI scanner: for both actuation and visualization. When applying rotating homogeneous magnetic fields, the swimmer performs an axial movement due to its shape and the viscosity of the surrounding medium. These fields can be generated with an MPI scanner. The swimmer dynamics have been observed and a maximum swimming velocity of 6 mm/s at a rotation frequency of the magnetic field of 10 Hz was found. The experiments are performed with a commercially available preclinical MPI scanner. It is shown, that the swimmer is suitable to be imaged with MPI. Furthermore, sequentially acquired images of a moving swimmer are shown. For this, the MPI scanner was alternately driven in imaging and actuation mode.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Huarui Fu, Yunlong Li, Li Ma, Caiyin You, Qing Zhang, Na Tian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The polycrystalline CoFeMnSi alloy with a potential spin gapless semiconductor (SGS) behavior was prepared by arc melting. The structures, magnetism and transport properties of CoFeMnSi alloy were investigated in detail. The occurrence of (1 1 1) superlattice XRD peak indicates the highly ordered Y-type structure of CoFeMnSi alloy. The saturation magnetization is around 3.49 〈em〉μ〈/em〉〈sub〉B〈/sub〉/f.u. and the Curie temperature is about 763 K. The transport properties exhibit a semiconducting-like behavior and the resistivity is about 269 μΩ cm at 300 K. The carrier concentration almost shows a non-dependence of temperature, which is different from that of traditional semiconductor, presenting a typical characteristic of spin gapless semiconductor. The carrier concentration and carrier mobility measured at 300 K are 4.9 × 10〈sup〉20〈/sup〉 cm〈sup〉−3〈/sup〉 and 46 cm〈sup〉2〈/sup〉/V.s, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): V.N. Gaonkar, E.T. Dias, Arka Bikash Dey, Rajendra Prasad Giri, A.K. Nigam, K.R. Priolkar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper we attempt to understand the role of tin and carbon in magnetic interactions in Mn〈sub〉3〈/sub〉SnC. Mn〈sub〉3〈/sub〉SnC exhibits a time dependent magnetic configuration and a complex magnetic ground state with both ferromagnetic and antiferromagnetic orders. Such a magnetic state is attributed to presence of distorted 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si33.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉Mn〈/mtext〉〈/mrow〉〈mrow〉〈mn〉6〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉C octahedra with long and short Mn–Mn bonds. Our studies show that C deficiency increases the tensile strain on the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si33.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉Mn〈/mtext〉〈/mrow〉〈mrow〉〈mn〉6〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉C octahedra which elongates Mn–Mn bonds and strengthens ferromagnetic interactions while Sn deficiency tends to ease out the strain resulting in shorter as well as longer Mn–Mn bond distances in comparison with stoichiometric Mn〈sub〉3〈/sub〉SnC. Such a variation strengthens both, ferromagnetic and antiferromagnetic interactions. Thus the structural strain caused by both Sn and C is responsible for complex magnetic ground state of Mn〈sub〉3〈/sub〉SnC.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 474〈/p〉 〈p〉Author(s): A. Rathi, P.D. Babu, P.K. Rout, V.P.S. Awana, Vikash K. Tripathi, R. Nagarajan, B. Sivaiah, R.P. Pant, G.A. Basheed〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present the results of a detailed investigation of magnetism in spinel chromite NiCr〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 magnetic nanoparticles (MNPs). Compared to the bulk NiCr〈sub〉2〈/sub〉O〈sub〉4〈/sub〉, the finite crystallite size of about 10 nm lowers the Jahn-Teller distortion and greatly enhances the collinearity of the spin structure in MNPs with considerably reduced “frustration index” = 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si45.gif" overflow="scroll"〉〈mrow〉〈mo stretchy="false"〉|〈/mo〉〈msub〉〈mrow〉〈mi〉θ〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉CW〈/mi〉〈/mrow〉〈/msub〉〈mo stretchy="false"〉|〈/mo〉〈/mrow〉〈/math〉/〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si46.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉. This leads to (longitudinal) ferrimagnetic ordering at much higher temperature, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si47.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉c〈/mi〉〈/mrow〉〈/msub〉〈mo〉≈〈/mo〉〈mn〉100〈/mn〉〈/mrow〉〈/math〉 K and suppression of (transverse) antiferromagnetic ordering in MNPs (cf. 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si46.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si42.gif" overflow="scroll"〉〈mrow〉〈mo〉≃〈/mo〉〈/mrow〉〈/math〉 65 K and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si50.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si42.gif" overflow="scroll"〉〈mrow〉〈mo〉≃〈/mo〉〈/mrow〉〈/math〉 30 K in the bulk); a transition to the cluster spin glass state occurs at 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si52.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉g〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 = 19.0 K. Moreover, the M-H hysteresis loops show anomalous “hour-glass” behavior at fields near 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si53.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉H〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 in the vicinity of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si52.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉g〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉; this non-monotonous 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si53.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉H〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (T) variation can not be accounted from the celebrated Stoner-Wohlfarth model. The present study interprets the anomalous 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si53.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉H〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (T) behavior in the framework of magnetically interacting core-shell structure with large surface anisotropy, and points out the importance of surface effects in nanochromites compared to their counterpart ferrites.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Anna Konopacka, Rafał Rakoczy, Maciej Konopacki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bioethanol is a promising liquid biofuel, which can be produced from the wide range of biomass feedstock by the fermentation process with the 〈em〉Saccharomyces cerevisiae〈/em〉 yeast. The application of the rotating magnetic field (RMF) is one of the possibilities to increase the efficiency of the process. Therefore, the magnetically-assisted bioreactor equipped with RMF generator was used to perform the ethanol fermentation process with the sugar-rich medium. Moreover, the yeast cells were modified by addition of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanoparticles. The obtained data suggested that the stimulation of applied cells with RMF did increase the proliferation and the ethanol production process. Furthermore, the calculated maximum specific growth rate and the productivity coefficient showed RMF positive effect on this magnetically-assisted bioprocess. The stimulation was found as ruled by field frequency (connected with magnetic induction of RMF) and it was revealed that the process productivity was higher for experiments with modified cells and the growth rate was higher for the process without the addition of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanoparticles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Alimohammad Mesbahinia, Mohammad Almasi-Kashi, Ali Ghasemi, Abdolali Ramezani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper Co〈sub〉1-x〈/sub〉Ni〈sub〉x〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 in which x ranging from 0.0 to 1.0 with 0.2 intervals was prepared with different particle size using a co-precipitation method. A single phase cubic spinel structure with an average crystallite size between 24 and 34 nm was obtained. X-ray diffraction, fourier transform infrared spectroscopy, field emission scanning electron microscopy and vibration sample magnetometer were used to characterize the samples. The energy dispersive X-ray analysis was in good agreement with the nominal composition. It was found that the functional groups of Co-Ni spinel ferrite were formed during the combustion process. It was found that by substitution of nickel cation in cobalt ferrite, the saturation magnetization and the coercivity decreased from 52.70 emu/g and 1673 Oe to 22.11 emu/g and 134 Oe, respectively. First order reversal curves were employed to map the magneto-static interactions and coercivity distributions as a function of nickel concentration. Adding nickel shifts the switching field distribution to the lower field thereby softening the samples. The ratio of reversibility increases with an increase in nickel content due to increase in the percentage of superparamagnetism.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): P. Wongjom, R. Ramos, S. Pinitsoontorn, K. Uchida, E. Saitoh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Measurements of transverse thermoelectric voltage were carried out in Co〈sub〉40〈/sub〉Fe〈sub〉60〈/sub〉 (CoFe)/Yttrium-Iron-Garnet (YIG) magnetic junctions, using the CoFe film as the spin detector. An unusual dependence of the voltage on the CoFe thickness was observed in the in-plane magnetized (IM) configuration; the junction with a relatively thick CoFe layer (40 nm) exhibits positive signals, whereas the junctions with a thinner CoFe layer (7-10 nm) exhibit negative signals. To find the origin of the behavior, we compare the voltage signals in the CoFe/YIG and CoFe/GGG systems in the IM configuration as well as perpendicularly magnetized (PM) configuration. Furthermore, the anomalous Hall effect was also measured in the Hall-bar shaped CoFe films. The experimental results suggest that the observed thickness dependence of the voltage is attributed to the combination of the inverse spin Hall effect (ISHE) and the anomalous Nernst effect (ANE) in the CoFe layers; the former shows a negative voltage and its contribution gradually increases with decreasing the CoFe thickness, whereas the latter shows a positive and mostly thickness independent voltage. The competition between the ISHE and ANE contributions results in the observed peculiar CoFe-thickness dependence of the transverse thermoelectric voltage.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 472〈/p〉 〈p〉Author(s): Jian Lei, Jingwu Zheng, Haida Zheng, Liang Qiao, Yao Ying, Wei Cai, Wangchang Li, Jing Yu, Min Lin, Shenglei Che〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we investigated the effects of heat treatment and lubricant on the magnetic properties of iron-based soft magnetic composites by one-pot synthesis method. Scanning electron microscopy (SEM) revealed that the surface of the coated Fe powder was coated with different thickness of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 insulating layer. The experiment results indicated that using lubricant in the coated iron-based compacts presented higher permeability, higher resistivity, lower core loss over the wide frequency range compared with those without using lubricant after heat treatment at 773 K. The above effects would be reduced with the increase of the thickness of the alumina coating. As the heat treatment temperature raised from 573 K to 773 K and even higher 873 K, zinc stearate continued to decompose, and its decomposition product carbon reacted with the iron oxide of the thinner coating. As a result, the frequency stability of the permeability decreased especially at high frequencies, the resistivity decreased significantly, and the eddy current loss increased significantly. When the alumina insulation layer became thick, the effects of zinc stearate and its leaving carbon after decomposition on the properties of the pressed magnet decreased.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The above schematic diagram can be clearly stated: With the heat treatment temperature increasing, the change of the lubricant and the alumina insulation layer the and its effects on the properties of the alumina-coated iron-based SMCs material are well explained.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S030488531832331X-ga1.jpg" width="417" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 April 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 475〈/p〉 〈p〉Author(s): Ch. Gritsenko, A. Omelyanchik, A. Berg, I. Dzhun, N. Chechenin, O. Dikaya, O.A. Tretiakov, V. Rodionova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We demonstrate how the configuration and magnitude of a magnetic field, applied during magnetron sputtering of a NiFe/IrMn bilayer, influence the magnetic properties of the structure, such as hysteresis loop shape, coercivity, and exchange bias. Furthermore, we illustrate that it is possible to create a stepwise hysteresis loop in the sample’s region with the highest field gradient. The found features can be used for future sensor applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): E.A. Zvereva, T.M. Vasilchikova, M.I. Stratan, S.A. Ibragimov, I.S. Glazkova, A.V. Sobolev, A.N. Vasiliev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉X-band ESR technique has been successfully applied to study 〈em〉S〈/em〉 = 1/2 spin chain compound vanadyl diacetate VO(CH〈sub〉3〈/sub〉COO)〈sub〉2〈/sub〉. Parameter of the intrachain interactions for uniform Heisenberg antiferromagnetic chain amounts to 〈em〉J〈/em〉/〈em〉k〈sub〉B〈/sub〉〈/em〉 = −167 К, while the ratio between the interchain (〈em〉J〈/em〉′ 〈 0.02 К) and intrachain interactions in this compound reaches a remarkably low value 〈em〉k〈/em〉 = 〈em〉J〈/em〉′/〈em〉J〈/em〉 ∼ 10〈sup〉−4〈/sup〉. Our findings are in consistence with spin-singlet quantum ground state.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): S.L. Hu, J. Liu, H.Y. Yu, Z.W. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nano-powders with controllable particle size, excellent magnetic properties and thermal stability of barium hexaferrite (BaFe〈sub〉12〈/sub〉O〈sub〉19〈/sub〉) have been synthesized via a co-precipitation/calcination technique. The phase composition, morphology and magnetic/thermal properties of the products were systematically studied. XRD patterns reveal that a long co-precipitation reaction time (5 h) and high calcination temperature (1100 °C) are beneficial for the formation of BaFe〈sub〉12〈/sub〉O〈sub〉19〈/sub〉 phase and decreasing the tendency to agglomeration. SEM micrographs show that the products show a hexagonal flake-like particle shape and the size are well controlled and maintained at single-domain particle size range area (〈460 nm), above which the coercivity will decrease abruptly for the coupling exchange among particles. The products with 〈em〉〈sub〉j〈/sub〉H〈sub〉c〈/sub〉〈/em〉 of 5934 Oe, temperature coefficient of remanence (〈em〉α〈sub〉Br〈/sub〉〈/em〉) of −0.176% K〈sup〉−1〈/sup〉 and temperature coefficient of coercivity (〈em〉β〈sub〉jHc〈/sub〉〈/em〉) of 0.0427% K〈sup〉−1〈/sup〉 were obtained when co-precipitated for 5 h and calcined at 900 °C for 2 h. A high saturation magnetization of 66.9 emu/g was obtained when co-precipitated for 5 h and calcined at 1100 °C for 2 h, approaching the theoretical saturation magnetization (72 emu/g).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 472〈/p〉 〈p〉Author(s): Prabhanjan D. Kulkarni, P.V. Sreevidya, Jakeer Khan, P. Predeep, Harish C. Barshilia, P. Chowdhury〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The M-H hysteresis curves of field cooled CoFe/FeMn bilayers and CoFe/FeMn/CoFe trilayers were studied to understand the exchange bias phenomena in these systems. The measured data revealed that the values of the exchange bias corresponding to a bottom CoFe layer reduced by about 23.5% with an addition of another CoFe layer at the top of bilayer stack. It was also observed that, while this reduction in exchange bias of a bottom CoFe layer (calculated in %) depends on thicknesses of a top CoFe layer and an antiferromagnetic FeMn layer, it is independent of the thickness of bottom CoFe layer. As the strength of exchange bias depends on the presence of pinned uncompensated moments in an antiferromagnetic layer, our observations indicate that the FeMn layer consists comparatively lower amount of pinned uncompensated moments in trilayers. This reduction in pinned uncompensated moments of FeMn layer in trilayers is then co-related with the domain wall suppression in the FeMn layer in CoFe/FeMn/CoFe trilayers.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Sahar Oroujizad, Mohammad Almasi-Kashi, Sima Alikhanzadeh-Arani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉CoNi binary alloy nanoparticles were prepared by using a polyol method. The effect of the Cu additive (acting as the third element) on structural and magnetic properties of the CoNi〈sub〉50−x〈/sub〉Cu〈sub〉x〈/sub〉 (10 ≤ x ≤ 40) alloy was then studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), magnetometry and first-order reversal curve (FORC) analyses. It was found that a combination of Co-Ni alloy and Cu phases is formed when increasing the Cu content by x = 10 and 20. However, for x = 30 and 40, the resulting compound is obtained in the form of a single-phase ternary alloy. Increasing the Cu content increases the separation between soft and hard phases in the FORC diagram, leading to two distinct magnetic phases in CoNi〈sub〉10〈/sub〉Cu〈sub〉40〈/sub〉. The FORC data showed that the magnetic interaction between particles was reduced when increasing the Cu content. The reversible and irreversible components of the compounds were also estimated. The FESEM images showed the formation of ordered spherical CoNi alloy grains with a diameter of about 400 nm, comprising tight nanoparticles with sizes below 100 nm. Moreover, in the presence of the element Cu, a variation in the nanoparticle size and morphology was seen clearly.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Saadia Rasheed, Rafaqat Ali Khan, Faheem Shah, Bushra Ismail, Jan Nisar, Syed Mujtaba Shah, Abdur Rahim, Abdur Rahman Khan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A series of Li-Cd doped cobalt ferrites CoLi〈sub〉x〈/sub〉Cd〈sub〉x〈/sub〉Fe〈sub〉2-2x〈/sub〉O〈sub〉4〈/sub〉(x= 0.05, 0.1, 0.15, 0.2, 0.25) has been synthesized by hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB) as capping agent. XRD data has confirmed the formation of single crystalline cubic phase with average crystallite size of synthesized samples between 24-28nm. For all the samples the resistivity was found to increase with increase in dopants concentration with highest value of 7.3〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mo〉×〈/mo〉〈/math〉 10〈sup〉7〈/sup〉ohm.cm at Li-Cd content x= 0.1. Dielectric constant values of all the samples follow the typical Maxwell-Wagner type dispersion due to interfacial polarization and were observed to decrease with increase in frequency, which is a typical phenomenon in ferrites. The coercivity (〈em〉H〈sub〉c〈/sub〉〈/em〉), saturation magnetization (〈em〉M〈sub〉s〈/sub〉〈/em〉) and remanent magnetization (〈em〉M〈sub〉r〈/sub〉〈/em〉) of all the samples increase with dopant content, with maximum values of 936 Oe, 54 emug〈sup〉-1〈/sup〉 and 30 emug〈sup〉-1〈/sup〉 respectively at x=0.1. The obtained data with improved coercivity, saturation magnetization and remanent magnetization make Li-Cd doped cobalt ferrites as suitable materials for utilization in transformer cores and transmission lines.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Diana L. Torres, Paulo A. Suzuki, Daniel R. Cornejo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Novel heterostructures of Ni〈sub〉x〈/sub〉Ti〈sub〉1-x〈/sub〉/Ni and Ni〈sub〉x〈/sub〉Ti〈sub〉1-x〈/sub〉/Co, with 0.48 〈 x 〈 0.51 grown on Si (100) substrates using DC magnetron co-sputtering were investigated by SQUID magnetometry in the temperature range 10-400 K. The magnetic measurements showed an anomalous enhancement of the total magnetic moment and changes in the coercivity with temperature. These results are attributed to interfacial strain during the structural phase transition of NiTi and evidence the magnetoelastic coupling on these heterostructures. The anomalous enhancement in the magnetic moment is explained in terms on the additional anisotropy in the ferromagnetic layer induced by the interfacial stress. Such heterostructures attached to silicon can be thought of as potential devices for controlling magnetic properties by temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 29 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Olaf Kosch, Hendrik Paysen, James Wells, Felix Ptach, Jochen Franke, Lucas Wöckel, Silvio Dutz, Frank Wiekhorst〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉To aid the optimization and development of Magnetic particle imaging (MPI), an accurate and translatable apparatus and a methodology for the characterisation of imaging quality are required. This requires magnetic nanoparticles (MNP) as imaging tracer for MPI measurements in a long-term stable, defined state, since MNP in liquid suspension might tend to change their magnetic properties over time, e.g. as a result of particle aggregation, sedimentation, or disintegration. To this end, we have developed solid phantoms containing freeze-dried perimag in mannitol for the comparison of resolution capabilities between different MPI scanners. Freeze drying of MNP was determined to be the optimal immobilisation method for maintaining the dynamic magnetic properties of MNP as compared with polymer or starch techniques.〈/p〉 〈p〉Freeze-drying preserves the particle distribution, preventing the particles from aggregation or precipitation. Two different types of phantoms were developed, one (cross shaped) to seek for artefacts within reconstructed images, and one (coil shaped) to test the resolution limit. The resolution limit is determined from the coil phantom by measuring the smallest resolvable gap between the two adjacent tracer regions. Our resolution phantom contained a 2 mm wide channel filled with tracer. By using this phantom, the imaging performance of the preclinical MPI system and a prototype gradiometric separate receive coil installed within the same MPI scanner was determined. We found 2.1-2.2 mm resolution limit using the conventional set-up and 0.5-0.6 mm for the separate receive coil resulting in an improvement by factor four. Additionally, the resolution dependency on the channel wide was tested by a second resolution phantom contained a 1 mm wide channel. The long-term stability of the phantoms will be continuously monitored and improved.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 472〈/p〉 〈p〉Author(s): Andrzej Pawlak, Rıza Erdem, Gül Gülpınar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The expressions for dynamic (complex) dipolar and quadrupolar susceptibilities are obtained within the framework of the linear theory of irreversible thermodynamics in the Blume-Emery-Griffiths model. Frequency, temperature as well as crystal field dependences of the dispersion relations and absorption factors are investigated for two different phase diagram topologies which take place for K/J = 3 and K/J = 5.0. Their behaviors near the second- and first-order transition points as well as multi-critical points such as tricritical, triple and critical endpoint are presented.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): S. Morteza Mousavi, A. Ali Rabienataj Darzi, Omid ali Akbari, Davood Toghraie, Ali Marzban〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the influence of a non-uniform magnetic field on biomagnetic fluid flow in a duct with a constriction is investigated numerically. The magnetic field is generated by a wire carrying electric current located outside the duct. The biomagnetic fluid dynamics model, which is based on the ferrohydrodynamics and magnetohydrodynamics, is used to study the fluid flow, and a computational grid properly covering the magnetic field is used for the simulation. In this investigation, the influence of magnetic field on biomagnetic fluid flow in various percentages of the duct constriction, and the effect of the magnetic field on the biomagnetic fluid flow in various strengths of magnetic force are studied. The magnetic field is spatially varying, and the magnetic field strength decreases by increasing the distance from the wire carrying electric current which is the magnetic source. The results show that, the influence of the magnetic field on biomagnetic fluid flow is considerable near the magnetic source. Applying the magnetic field with enough strength causes the recirculation areas downstream of constriction to become smaller. In addition, applying the magnetic field has significant effects on the wall shear stress, so that it can decrease the shear stress on the wall away from the magnetic source.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): G. Frajer, O. Isnard, H. Chazal, G. Delette〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This paper investigates the effect of the cobalt addition on the magneto-crystalline anisotropy parameter of some polycrystalline ferrites. Magnetization curves have been experimentally determined at different temperatures on Ni〈sub〉1−x〈/sub〉Zn〈sub〉x〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 sintered samples with or without cobalt addition. In each case, a law of approach to saturation has been fitted to the measured data in order to extract the anisotropy parameter 〈em〉K〈sub〉1〈/sub〉〈/em〉 representative for the polycrystalline material.〈/p〉 〈p〉Besides, measurement of the complex susceptibility and power core-loss up to 5 MHz has been performed. This approach allows a discussion on the role of cobalt addition on the power core-loss mitigation. It has been found that the substitution with 0.02 mol. of Co leads to a small decrease in the 〈em〉K〈sub〉1〈/sub〉〈/em〉 values. This evolution is consistent with the rise in the rotational permeability. However, the change in 〈em〉K〈sub〉1〈/sub〉〈/em〉 cannot account for the core-loss reduction with Co. Rather, it is confirmed that Co hinders the domain wall displacement and subsequent dissipation up to an induction level that depends on the grain size.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Lixia Zhang, Qinlu Zhang, Min Gao, Zhiyi Luo, Ying Zhang, Xiaoxia Li, Kai Hua, Chao Zhang, Wenting Lai, Yali Cui〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Objective〈/h6〉 〈p〉To investigate the consistency between GoldMag® immunochromatography and immune scatter turbidimetry in hs-CRP detection.〈/p〉 〈/div〉 〈div〉 〈h6〉Methods〈/h6〉 〈p〉The data of hs-CRP were collected from 78 hospitalized patients, and these patients were divided into fingertip blood group and the venous blood group according to the different blood collection methods. The whole blood and plasma level of hs-CRP was detected by GoldMag® immunochromatography and immune scatter turbidimetry. Correlation analysis was carried out to compare the data of hs-CRP obtained by different approaches.〈/p〉 〈/div〉 〈div〉 〈h6〉Results〈/h6〉 〈p〉In both fingertip blood group and venous blood group, the concentration of hs-CRP determined by GoldMag® immunochromatography were positively correlated with those found with immune scatter turbidimetry. There was no significant difference in the level of hs-CRP provided by these two different approaches. (P 〉 0.05).〈/p〉 〈/div〉 〈div〉 〈h6〉Conclusion〈/h6〉 〈p〉GoldMag® immunochromatographic assay has good uniformity with immune scatter turbidimetry Scatter Turbidimetric Method for hs-CRP detection. Based on the double antibody sandwich method, antibody labeled GoldMag nanoparticles capture hs-CRP from whole blood or plasma and aggregate in test line of test strip. The magnetic intensity of agglomerated GoldMag® nanoparticles collected is measured by magnetic quantitative immunoassay analyzer. The concentration of hs-CRP can be obtained according to the standard curve between concentration and magnetic intensity. GoldMag® immunochromatography is served as an easy operation, high accuracy and stable method.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 29 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): N.Yu. Pankratov, V.I. Mitsiuk, V.M. Ryzhkovskii, S.A. Nikitin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The equiatomic intermetallic alloy MnZnSb with a tetragonal Cu〈sub〉2〈/sub〉Sb-type crystal structure (space group P4/nmm) was melted in the resistance furnace in the evacuated quartz ampoule. The adiabatic temperature change 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.gif" overflow="scroll"〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉ad〈/mi〉〈/mrow〉〈/msub〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈/math〉 and the isothermal variation of the magnetic entropy (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉M〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉) of the MnZnSb compound near to the magnetic phase transition were studied. The 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉ad〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 in a magnetic field up to 1.25 T was studied by the direct method. It was found that temperature dependencies of both 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉ad〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉S〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉M〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 show a sharp peak near room temperature with a maximum at Curie temperature 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉C〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 = 317 K. It was shown that there is no temperature hysteresis of the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉ad〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 in MnZnSb, and the maximum of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉ad〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 when the compound is heated or cooled is detected at the same temperature. The estimated value of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉ad〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 in a field of 14 T is 4.5 K. It was shown that near the Curie temperature, the field dependence of the maximum of magnetic entropy change is adequately described by the thermodynamic Landau theory for magnetic second-order phase transitions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Jian-feng Zhou, Song Zhang, Feng Tian, Chun-lei Shao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic particles (MPs) have good response to external magnetic field. To investigate the motion regularity of MPs in a mcirochannel flow governed by alternating gradient magnetic field, a 3D numerical simulation method is established based on the lattice Boltzmann method (LBM) and the immersed boundary method (IBM). The motions of both a single MP and a short chain of MPs are investigated and each is found to be a superposition of transverse oscillation and longitudinal translation. By performing a simple filtering processing for the original trajectory of MP, it is revealed that the oscillation of MPs affected by alternating gradient magnetic field can be characterized as the simple harmonic vibration. The oscillation frequency of MPs is basically in accordance with the alternating frequency of the gradient magnetic field in the range from 400 to 800 Hz. The larger magnetic field gradient results in the larger amplitude of oscillation. The wavelength of the trajectory is increased due to the increasing inlet velocity of carrier fluid. For the MP chain, both the period and amplitude of oscillation will decrease with the increase of alternating frequency of magnetic field. The turbulence intensity distribution indicates that the turbulence of microchannel flow can be enhanced by the oscillation of MPs thus enhance the mass or heat transfer in the carrier fluid.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): Zuzana Bednarikova, Jozef Marek, Erna Demjen, Silvio Dutz, Maria-Magdalena Mocanu, Josephine W. Wu, Steven S.-S. Wang, Zuzana Gazova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉More than 50 diseases are associated with a conversion of proteins or peptides from their soluble functional states to highly organized fibrillar aggregates called amyloid fibrils. Due to the specific physico-chemical properties, specifically designed iron oxide nanoparticles may be an effective strategy for inhibiting the amyloid fibrillization of proteins. The inhibitory effect of three types of iron oxide nanoparticles coated with differently modified dextran on lysozyme fibrils formation was studied by Thioflavin T assay and atomic force microscopy. The size and zeta potential of studied nanoparticles were determined by dynamic light scattering. It had been found that nanoparticles are able to inhibit formation of lysozyme amyloid aggregates in concentration-dependent manner. Our results suggest that size of nanoparticles influenced the extent of their inhibitory properties. Moreover, the most effective nanoparticles were not toxic after 48 h incubation with neuroblastoma SH-SY5Y cell line at concentration close to IC〈sub〉50〈/sub〉 values.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 473〈/p〉 〈p〉Author(s): X.W. Dong, R.F. Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The chirality-dependent propagations of transverse domain walls (DWs) in two types of Y-shaped nanostrips under small driving fields were investigated using micromagnetic simulations. They both exhibit the well DW chirality selection behaviors and the hugely reduced DW transmission fields owing to the specific magnetic charge distributions on both the junction and corners. The DW transmission field even can be as small as 2 Oe. Additionally, the DW chirality can be controlled by applying an out-of-plane field, leading to the use of the Y-shaped nanostrips as logic devices, such as selector, rectifier and amplifier.〈/p〉〈/div〉 〈/div〉