ALBERT

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Dongyang Zhu, Yuan Xu, Xiaoxiong Wang, Jinxia Sui, Qi Liu, Chao Song, Jing Yu, Junpeng Wu, Yunze Long〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We systematically studied the structure, electrical and magnetic properties of indium oxide prepared by electrospinning. Resistance studies have shown that indium oxide nanofibers have significant extrinsic effects. Magnetic studies have shown that indium oxide has obvious positive and negative magnetic resistance competition and transformation during temperature change. The conduction mechanism can be described using Mott’s variable range hopping conduction and the weak localization effect, where the dimensions of the conduction model are all in three dimensions.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Yunfeng Zhu, Biao Zhang, Jialiu Gu, Songjing Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To continuously perform pretreatment operations of biological detection reagents, a kind of microfluidic bioseparation chip that integrates mixer, heater and soft magnets for detection of nucleic acid and extraction of molecular proteins with magnetic beads methods is presented in the paper. A specific magnetic field is formed in a desired chamber bonded with PDMS and PMMA sheets by embedding soft magnets of iron powders in the chip, and magnetized by an external magnetic field. Soft magnets distributed in different ways are designed respectively, and the characteristics of the magnetic field, as well as the magnetic trajectory of the magnetic beads are simulated by considering the magnetic-fluid coupling. An experimental platform to observe the capturing of magnetic beads is built and the capture phenomenon for magnetic beads with lattice-distributed soft magnets is also experimentally verified. Based on the experimental data, the capture efficiency of the magnetic beads is calculated with the image processing method. The results show that lattice-distributed soft magnets are more effective than the array-distributed soft magnets for separating the magnetic beads. Furthermore, the lattice-distributed soft magnets can improve the separation efficiency of the detected reagent maintained to be more than 80% when the inlet flow rate increases from 0.01 m/s to 0.05 m/s.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Cameron Gibson, Steve Bildstein, Jewell Anne Lee Hartman, Marek Grabowski〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We examine a magnetic moment subject to a static external magnetic field and a time dependent driving magnetic field. Taking the system in the highly anisotropic limit, like that of a thin film, we lower the complexity of the system so that it may be analyzed for transitions to chaos analytically using the Melnikov method. Guided by the calculation of the Melnikov bifurcation functions we computationally calculated the Lyapunov characteristic exponents for several lines in parameter space and find that the Melnikov method is a good predictor of chaotic motion for sufficiently small external fields. Motion plots and Poincaré sections are also plotted for several parameter space points to observe the transitions to and from chaos around the calculated Melnikov bifurcations functions.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): F. Hu, J.L. Ni, S.J. Feng, X.C. Kan, R.W. Zhu, W. Yang, Y.J. Yang, Q.R. Lv, X.S. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉FeSi/glass composites with different glass content by using low melting glass as adhesive and insulating agent are prepared, and their magnetic properties are investigated. SEM morphology shows that the glass particles between different FeSi spheres deform into flakes after heat treatment, which reveals that glass powder acts as adhesive and insulating agent in the composites. The FeSi/glass composites have high saturation magnetization (up to 210 Am〈sup〉2〈/sup〉/kg), low magnetic losses (less than 2100 kW/m〈sup〉3〈/sup〉 at 100mT and 100 kHz) and moderate permeability. The moderate eddy current loss obtained by losses separation further indicates that the eddy current between different FeSi spheres is effectively blocked by glass. The advantages of this new preparation process of SMCs are also discussed.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Rui Zhang, Zsolt Gercsi, M. Venkatesan, Ajay Jha, Plamen Stamenov, J.M.D. Coey〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As-cast ingots of Mn〈sub〉100−x〈/sub〉Z〈sub〉x〈/sub〉 with Z = Al, Ge, Mn, Fe and Co all have the A13 βMn structure up to some maximum value of 〈em〉x〈/em〉. The magnetic susceptibility of pure βMn is ≈ 9 × 10〈sup〉−4〈/sup〉 from 4 to 400 K, but the field-cooled and zero-field-cooled susceptibilities of all doped samples increase at low temperature and they bifurcate at a spin-freezing temperature 〈em〉T〈/em〉〈sub〉f〈/sub〉 that increases with 〈em〉x〈/em〉, linearly at first. Point contact Andreev reflection shows evidence of a net spin polarization in a spin glass sample but not in the pure βMn spin liquid. Fixed-moment density functional calculations indicate a very shallow energy minimum (〈 1 meV/atom) for the 12〈em〉d〈/em〉-site Mn moment that extends from 〈em〉x〈/em〉 = 0 to 0.4 µ〈sub〉B〈/sub〉. The minimum energy is interpreted as a lower limit on the zero-point energy.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Yu Kuai Liu, Hon Fai Wong, Sheung Mei Ng, Chee Leung Mak, Chi Wah Leung〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We performed anomalous Hall effect (AHE) measurements in Pt/Tm〈sub〉3〈/sub〉Fe〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 (Pt/TmIG) bilayers grown on (1 1 0) and (1 1 1)-oriented Gd〈sub〉3〈/sub〉Ga〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 (GGG) substrates (Pt/110TmIG and Pt/111TmIG). Qualitative differences were observed in the two sets of samples: at low magnetic fields only Pt/111TmIG displays square AHE loop, while Pt/110TmIG exhibits non-hysteretic AHE behavior. Systematic temperature-dependent AHE measurements in Pt/111TmIG showed double switching events of AHE loops below 30 K, which was attributed to the larger moment of Tm〈sup〉3+〈/sup〉 sublattice at low temperatures and was consistent with earlier theoretical calculations [A. Lehmann-Szweykowska 〈em〉et al〈/em〉., Phys. Rev. B 37, 459 (1988)]. Our results confirmed the strong coupling of Tm〈sup〉3+〈/sup〉 magnetic moment with the lattice and the crucial role of the interfacial structure, suggesting a way to detect rare earth moment switching in iron garnets by electrical measurements.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Sok Kim, Kumchol Yun, Kwanghun Kim, CholJin Won, Kyongsu Ji〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a new general nonlinear magneto-elastic coupled constitutive model was proposed for soft ferromagnetic materials under magnetic field and pre-stress. The model is based on thermodynamic theory of magnetic materials and Jiles theory on magnetomechanical effect, considering demagnetization field. This model can accurately predict the changes of magnetostrictive strain and magnetization under pre-stress; in particular, it can obviously predict the nonlinear change of magnetostrictive strain according to compressive pre-stress. In addition, this model is concise by not including the inverse function of magnetization relationship and the piecewise function of stress in its mathematical form and can be degenerated to the previous general constitutive model for giant magnetostrictive materials. The prediction result by this model is well-consistent with experimental data. In comparison with the existing constitutive models for soft ferromagnetic materials, this model was demonstrated to have obviously-improved prediction accuracy, particularly in the compressive state. In conclusion, the proposed model can fully describe the effect of pre-stress on magnetostrictive strain and magnetization and the effects of magnetic field and pre-stress on Young’s modulus and relative magnetic permeability, reflecting the effect of demagnetization field on magnetomechanical characteristics.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): E.A. Popova, E.P. Chukalina, K.N. Boldyrev, A. Jablunovskis, I.A. Gudim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report on the high-resolution spectroscopic study of multiferroic ErFe〈sub〉3〈/sub〉(BO〈sub〉3〈/sub〉)〈sub〉4〈/sub〉. The energies of all eight Kramers doublets of the ground 〈sup〉4〈/sup〉I〈sub〉15/2〈/sub〉 multiplet of the Er〈sup〉3+〈/sup〉 ion were determined by the high-resolution 〈sup〉4〈/sup〉I〈sub〉13/2〈/sub〉 → 〈sup〉4〈/sup〉I〈sub〉15/2〈/sub〉 infrared luminescence spectra. The spectroscopically determined temperature dependence of the splitting of the ground Kramers doublet was used to calculate the contribution of the erbium subsystem into the specific heat and the magnetic susceptibility of erbium iron borate. The analysis of the thermodynamic properties based on these calculations allowed us to suggest the domain structure in the easy-plane antiferromagnetically ordered iron subsystem, with two magnetically nonequivalent erbium positions in each domain.〈/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-S0304885319326587-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Kaili Li, Danni Cheng, Hongya Yu, Zhongwu Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fe powders based soft magnetic composites (SMCs) with organic- inorganic multiple-layer coating were fabricated by improved isolation coating followed by pressing and curing. Phosphate and organic resin were selected as the insulting layers. The influences of phosphating process and the composition of organic coating on the magnetic properties of the SMCs and soft magnetic cores have been systematically investigated. The phosphating process was modified for simple and easy operation, suitable for carbonyl iron powders with small particle size. The optimized phosphating method created a complete and continuous phosphate layer on the surface of micron sized particles. Without resin coating, the magnetic cores fabricated with the phosphated powders prepared with 0.5–0.7 wt% phosphoric acid exhibit relatively high permeability and quality factor at high frequency. In addition, a new type of mixed resin with good thermal stability was employed for insolating coating, which provides distinctly higher resistivity and better protective effect than silicone. The optimal content of the mixed resin content is about 3 wt% for fabricating the magnetic cores with low eddy current loss and hysteresis loss by producing a protective layer to isolate magnetic particles and reduce the internal stress. The SMC cores prepared with optimized phosphating process and organic coating exhibit high relative density (93.7%), high electric resistivity (2.23 × 10〈sup〉7〈/sup〉 Ω·cm), stable permeability (in the frequency range from 5 to 1000 kHz), high quality factor (44.8 at 700 kHz) and relatively low magnetic loss (159.0 kW/m〈sup〉3〈/sup〉 at 100 kHz).〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 17 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): F.J.G. Landgraf, C. Ragusa, D. Luiz Rodrigues Junior, M.B.S. Dias, O. de la Barrière, F. Mazaleyrat, F. Fiorillo, C. Appino, L. Martino〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There is an increasing interest in the optimization of non-oriented electrical steels for applications under excitation frequencies above 400 Hz. We discuss in this paper the possibility of a new manufacturing procedure, where skin-pass and subsequent heat treatment for recovery are applied as the two last stages of sheet processing. Samples from a commercial non-oriented 3 wt% silicon steel were submitted to 2.5% thickness reduction and were heat treated at temperatures ranging between 600 and 850 °C for 2 hours. It is shown that, although the hysteresis loss increases with plastic deformation, the excess loss decreases in such a way that under increasing magnetizing frequencies the total energy loss of the deformed and recovered sample becomes lower than in the starting material. The higher the annealing temperature the lower the frequency at which crossover of the loss curves is observed, as long as full recrystallization does not occur. It is assumed that with the dislocation structures left in the deformed and partially recovered samples one achieves a condition of increased fragmentation of the magnetization process, that is, of increased number of concurring correlation regions (Magnetic Objects). The corresponding decrease of the excess loss component can eventually overcompensate the deterioration of the quasi-static magnetic properties, leading to lower total losses.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): J. Geshev, R.F. Lopes, J.L. Salazar Cuaila, L.L. Bianchi, A. Harres〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently, the in-field 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si50.svg"〉〈mrow〉〈mi〉δ〈/mi〉〈msub〉〈mrow〉〈mi〉M〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉R〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 interaction-plot technique has been extended for systems with shifted and asymmetric major magnetization hysteresis loops. In the present work an alternative definition of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si51.svg"〉〈mrow〉〈mi〉δ〈/mi〉〈msub〉〈mrow〉〈mi〉M〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉R〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, allowing a better graphic visualization of this plot, is given. The method is applied to a series of Co/Cu/IrMn films in order to examine the variations, with the thickness of the nonmagnetic Cu layer, of the interactions emerging from the Co/IrMn interface and those coming from magnetic coupling within the Co film. Model simulations indicate that, for the case of symmetric major loops, the effects of the ferromagnet/antiferromagnet exchange coupling might not be identified by interaction plots, being only evidenced by the shift along the magnetic-field axis and the coercivity enhancement.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 16 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Mansoureh Amanollahi, Mehdi Zamani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The properties of optimized transverse magneto-optical Kerr effect (TMOKE) of all-types of bi-gyrotropic metamaterials have been investigated and compared for both s- and p-polarized waves. We demonstrated that double-positive and double-negative ones are capable of achieving maximum TMOKEs, but with the opposite signs. On the other hand, single-negative metamaterials could not provide large TMOKE. In addition, a giant TMOKE can be observed in a special case of metamaterials whose are exhibiting near-zero refractive index. A large TMOKE response is important for applications in magneto-optical data storage and high-definition imaging.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Yurui Wei, Chen Liu, Xiangqian Wang, Huiliang Wu, Haiyan Xia, Zhaozhuo Zeng, Jianbo Wang, Jiangwei Cao, Qingfang Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-frequency studies, of exchange-coupled multilayer films, are the key to advance the development of fast switching spintronic devices. In this paper, we utilize the first-order reversal curve (FORC) to improve the understanding of the spin-reorientation transition process when the permalloy (Py) thickness increases. We also investigate the temperature dependence of the high-frequency properties of exchange-coupled [Co/Pd]〈sub〉6〈/sub〉/Py (t nm) multilayer films during the spin-reorientation transition (SRT). The results show that the phase state of the magnetic domain changes, from the perpendicular phase to the multi-domain phase as the Py layer increases during the SRT. The temperature-dependent high frequency results indicate that the resonance linewidth ΔH〈sub〉res〈/sub〉 increases gradually when the temperature decreases from 300 K to 50 K. Our experimental study offers new insight into the SRT process in exchange-coupled multilayer films and can help to promote the development of fast switching spintronic devices.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): J. Krishnamurthy, A. Venimadhav〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the structural, transport, pyrocurrent and magnetic behaviors of Eu〈sub〉2〈/sub〉CoMnO〈sub〉6〈/sub〉 (ECMO) sample are reported. It was prepared by the solid-state reaction method and crystallized in monoclinic crystal structure with a space group of P2〈sub〉1〈/sub〉/n. A systematic study of the temperature and magnetic field-dependent susceptibility revealed a complex magnetic behavior with field-induced type-II metamagnetic phase transition of the first-order. The multiple sharp jumps in the initial magnetization curve for T 〈 10 K could be attributed to structural distortion related to the martensite-like strains from E*-type antiferromagnetic to ferromagnetic ordering. The metastable magnetic behavior for T ≥ 60 K is ascribed to a transformation of the low-field disordered spin glass phase to long-range ordered ferromagnetic phase, induced by critical fields. These critical fields are quite sensitive to the direction and magnitude of the field-cooling process. The temperature-dependent magnetocaloric effect with maximum value of ~3.3 J kg〈sup〉−1〈/sup〉 K〈sup〉−1〈/sup〉 at T〈sub〉C〈/sub〉 ~ 123 K and the electrical transport behavior of ECMO were studied. Further, temperature dependent pyroelectric current and polarization data of ECMO are investigated.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 14 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): O. Maloberti, M. Nesser, E. Salloum, S. Panier, J. Fortin, P. Dassonvalle, C. Pineau, T. Nguyen, J-P. Birat, I. Tolleneer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this contribution, we propose to cope with the problem of soft magnetic materials heterogeneity and non-uniformity in terms of domains structure. This non-uniformity expresses itself with space variations of domains and walls geometry and characteristic properties from the bulk towards the surface. We investigate the possibility of describing and predicting these changes from a mesoscopic point of view. We begin with an introduction of typical subdivisions and define a tensor state variable [Λ〈sup〉2〈/sup〉] to represent the diversity of magnetic structures with domains and walls. We then explain the material structuring thanks to an energy balance between the mesoscopic magnetic exchange, magneto-crystalline anisotropy, self-magnetostriction anisotropy, stress induced anisotropy and the dipolar demagnetizing energy. We write every contribution as a function of [V〈sup〉2〈/sup〉]=[Λ〈sup〉2〈/sup〉]〈sup〉-1〈/sup〉. After minimizing the total energy, we derive a formulation compatible with classical numerical methods. [Λ〈sup〉2〈/sup〉] is deduced thanks to a partial differential equation and surface boundary conditions. When a time varying field is applied to the material, damping effects occur either in the mass or at the surface. Eddy currents induced within domains lead to consider a volume dissipation energy. The surface magnetic field is also dampened by both the static hysteresis mainly due to defects and the dynamic hysteresis which stems from eddy currents around magnetic walls, added to the an-hysteretic field. The surface magnetic field, magnetic structure, and thus the polarization being known on the external surface, time variations of the volume magnetic structure can be calculated within the mass. Using the static or dynamic magnetic field coupling at the surface, the magnetic polarization can be rebuilt in the mass to calculate the apparent magnetic permeability. Finally, finding the geometry and frequency dependent vector magnetic behavior and iron losses becomes possible. The tensor magnetic phase theory is able to account for the sensitivity of the magnetic structure to the geometry, the macroscopic anisotropy partly influenced by the metallography, the residual or induced stress, some surface effects such as the texture, the rugosity or even any scribing patterns, at a mesoscopic scale. Two test cases for GO and NGO electrical steels are presented. Sensitivity analysis on the test case with GO steel are discussed. Results are then compared to static and dynamic measurements of GO SiFe sheet samples. This paper contributes to the investigations carried out on the geometry dependent magnetic behavior of soft magnetic materials.〈/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-S0304885319327933-ga1.jpg" width="292" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Zohaib Manzoor, Ayesha Khalid, Ghulam M. Mustafa, Shahid M. Ramay, Shahzad Naseem, Shahid Atiq〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Interfacial coupling in heterostructures of spinel-perovskite nanocomposites, primarily controls the performance of the multiferroic samples, especially in such type of binary structure systems. The interfacial response in this class of composites is a key feature to enhance the magnetoelectric response of the materials. For this purpose, here we synthesized a series of 0.5BiFeO〈sub〉3〈/sub〉−0.5Ni〈sub〉0.5〈/sub〉Co〈sub〉0.5〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 by substituting Zn at Co-site in spinel phase, using a facile wet chemical technique. The structural analysis carried out using X-ray diffraction revealed the presence of both the phases. Spherical type agglomerated grains with sharp and distinct grain boundaries were exposed by field emission scanning electron microscopy. Elemental profile was mapped by energy dispersive X-ray spectroscopy to confirm the stoichiometric composition of these composites. Improvement in saturation magnetization and remanence with increasing substitution contents was analyzed via vibrating sample magnetometer. In addition, the ferroelectric investigations were carried out to calculate the recoverable energy and energy loss density. Magneto-polarizability investigations uncovered the potential of these composites for multi-state device applications.〈/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-S0304885319333438-ga1.jpg" width="265" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Chanki Lee, Hee Young Kwon, Nam Jun Kim, Han Gyu Yoon, Chiho Song, Doo Bong Lee, Jun Woo Choi, Young-Woo Son, Changyeon Won〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We use a Monte Carlo simulation to investigate the magnetic structures in a bilayer magnetic system containing a locally inverted interlayer coupling region. The stabilization of multiple magnetic structures, including the magnetic skyrmion, is possible in the locally inverted interlayer coupling region. Various factors such as the region area, anisotropy, interlayer coupling strength, and exchange coupling strength affect the properties of the structures, including their size and chirality. We obtain conditions for the stabilization and transitions of these magnetic structures. The Dzyaloshinskii-Moriya interaction (DMI) and dipolar interaction play prominent roles as they significantly enhance the formation and stability of the structures. An asymmetric feature can arise from the broken inversion symmetry in the structure formation, yielding an interfacial DMI, which stabilizes the skyrmion. It is demonstrated that the dipole interaction also acts as an effective interfacial DMI in the system.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 20 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Carlo Ragusa, Luigi Solimene, Salvatore Musumeci, Olivier de la Barriere, Fausto Fiorillo, Giulia Di Capua, Nicola Femia〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper we propose a calculation model for the analysis of the current waveform in ferrite power inductors subjected to large-signal square-wave voltage, a typical regime of present-day switch-mode power supplies. This kind of problem is characterized by the non-linear response of the inductor across a wide range of current values, up to the limit of inductor saturation. Consequently, non-linear differential equations must be adopted in the description of the circuit. In this paper, we solve the equations of the circuit through an effective iterative method, by which the current waveform is computed through successive approximations. These results are eventually verified by comparison with experiments performed on a commercial buck-type converter.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Daichi Ito, Hiroshi Yao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Plasmon-tuned magneto-optical (MO) properties enable design concepts of MO devices with various nanoarchitectures. In this study, magnetic circular dichroism (MCD) is presented in plasmonic-magnetic Au-Fe〈em〉〈sub〉3〈/sub〉〈/em〉〈sub〉−〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉O〈sub〉4〈/sub〉 heterodimer nanostructures dispersed in solution. The heterodimers are synthesized by thermal decomposition of Fe(III) precursors in the presence of preformed Au nanoparticles. The extinction spectrum exhibits a localized surface plasmon resonance (LSPR) peak, which is red-shifted with respect to the isolated Au particle resonance. On the other hand, the MCD response is overwhelmingly dominated by iron oxide counterparts consisting of multiphase magnetite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉)/maghemite (γ-Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉). No appreciable LSPR-enhancement in the MO response is found. As for the effect of the magnetic component on the LSPR behavior of Au, a decrease in the magnetoplasmonic response is observed. This suggests a reduction of the effective magnetic field to the Au counterparts, which can probably be due to magnetic shielding by the iron oxides in the near vicinity of Au nanoparticles.〈/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-S0304885319333906-ga1.jpg" width="265" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Xiaoli Zhang, Jian-Ping Zhou, Xi Yao, Zupei Yang, Guang-Bin Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There are few experimental studies on the shear-shear (S-S) mode magnetoelectric (ME) composites, especially near the resonance frequency because of their complex sample preparation and high resonance frequency. What’s more, theoretical studies on the S-S mode magnetoelectric composites is still blank. In this article, an equivalent circuit model was proposed to analyze the direct and converse magnetoelectric (DME and CME) effects in an S-S mode ME bilayered composite. Then, the composite was experimentally studied, showing a good agreement with the theoretical predication. The S-S mode has a remarkable field sensitivity and much high DME and CME coefficients, reaching 27.5 V/(cm·Oe) and 3 × 10〈sup〉-6〈/sup〉 s/m, respectively, in this simple bilayered composite under the DC magnetic field of 1800 Oe near the resonance frequency. The composite shows a prospect of applications in high frequency ME transducers, energy capture devices and magnetic field sensitive sensors.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Neil A. Salmon, Stephen R. Hoon〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A combined ferrite parametric amplifier and millimeter-wave homodyne interferometer are proposed as an ambient temperature Bell Test. It is shown that the non-linear magnetic susceptibility of the yttrium iron garnet (YIG) ferrite, on account of its narrow line-width Larmor precessional resonance, make it an ideal material for the creation of entangled photons. These can be measured using a homodyne interferometer, as the much larger number of thermally generated photons associated with ambient temperature emission can be screened out. The proposed architecture may enable YIG quantum technology-based sensors to be developed, mimicking in the millimeter-wave band the large number of quantum optical experiments in the near-infrared and visible regions which had been made possible by use of the nonlinear beta barium borate ferroelectric, an analogue of YIG. It is illustrated here how the YIG parametric amplifier can reproduce quantum optical Type I and Type II wave interactions, which can be used to create entangled photons in the millimeter-wave band. It is estimated that when half a cubic centimeter of YIG crystal is placed in a magnetic field of a few Tesla and pumped with 1 Watt of millimeter-wave radiation, approximately 10〈sup〉12〈/sup〉 entangled millimeter-wave photon pairs per second are generated by the spin-wave interaction. This means an integration time of only a few tens of seconds is needed for a successful Bell Test. A successful demonstration of this will lead to novel architectures of entanglement-based quantum technology room temperature sensors, re-envisioning YIG as a modern quantum material.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Kenny L. Alvarez, H.A. Baghbaderani, J.M. Martín, N. Burgos, M. Ipatov, Z. Pavlovic, P. McCloskey, A. Masood, J. Gonzalez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work demonstrates the high-frequency core loss performance of Fe-based amorphous and nanocrystalline powder cores, initially produced by gas atomised powder, consolidated using sieved particles ≤20 µm, and isolated by a precise insulating layer of polymer to limit the inter- and intra-particle eddy currents to attain enhanced performance. The large glass forming ability (GFA) of the gas atomised powder, reflected by different glass forming instruments, such as the supercooled region (Δ〈em〉T〈sub〉X〈/sub〉〈/em〉 = 54 °C) and the reduced glass transition temperature (〈em〉T〈sub〉rg〈/sub〉〈/em〉 = 0.56), is consistent with the substantial amorphisation capability of the alloy. To the best of our knowledge, this is the first-ever report to reveal a large Δ〈em〉T〈sub〉X〈/sub〉〈/em〉 in the Finemet-type alloy powders, an essential parameter to gas-atomise the amorphous powders with significantly lower cooling rates compared to the melt-spun ribbons. Further, subsequent annealing of the amorphous powders, between the exothermic events guided by differential scanning calorimetry (DSC), lead to the growth of a fine nanocrystalline structure of grains ≤15 nm, thanks to the positive enthalpy of mixing of Cu with the constituents to act as a nucleation agent, to retain the excellent soft magnetic properties. The DC soft magnetic properties of the powders were significantly improved on thermal annealing, confirmed by hysteretic loops, quantified by reduced coercivity 〈em〉H〈sub〉C〈/sub〉〈/em〉 〈1 Oe of annealed powders at 〈575 °C, and attributed to the reduced magnetoelastic contribution due to zero/near-zero magnetostriction anisotropy, attained due to the homogenous nanocrystalline structure. The amorphous and nanocrystalline powder cores, consolidated by compression moulding, show ultra-high loss performance, due to the ultra-low coercivity attained on nanocrystallisation, and negligible eddy currents loss, owning to efficient insulation of small particles, for high-frequency power conversion applications, such as voltage regulator (VR), and resonant converters, in automotive industry and data storage centres.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): S. Tamaru, N. Kikuchi, T. Igarashi, S. Okamoto, H. Kubota, S. Yoshida〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have developed a system to measure permeability over a wide frequency range with high sensitivity, which we call the transformer coupled permeameter. In this system, the magnetic sample is sandwiched by two short-terminated coplanar waveguides that form a loosely coupled transformer. In this way, the stimulus signal acting as a background becomes smaller as the frequency decreases, thus significantly suppressing the deterioration of the signal-to-noise ratio (SNR) at low frequencies that most conventional permeameters suffer from. It has been demonstrated that this system can provide a sensitivity high enough to measure the permeability of a single ferromagnetic flake particle comprising a noise suppression sheet over 10 MHz–20 GHz with a high SNR.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Fouzia Mashkoor, Abu Nasar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In recent years, several industries release varying concentrations of dye-containing wastewater directly into the ecosystem and become the foremost environmental concern. The adsorption method has been recognized to be one of the most effective techniques for the remediation of wastewater. The great efforts have been made by scientists to produce highly selective, discerning, and effective adsorbents. The introduction of magnetic iron oxide nanoparticles to adsorbents has led to a new avenue in resolving water pollution problems and found to have predominant significance in the elimination of dyes more efficiently compared to traditional adsorbents. Due to their unique physicochemical properties, magnetized adsorbents (magsorbents) display high removal efficiency along with easy and fast separation of adsorbent from aqueous media simply by applying an external magnetic field. Such a facile route of separation is crucial to increase the overall efficiency of operation and has great importance for practical application.〈/p〉 〈p〉This review summarizes the notable works carried out on the application of magsorbents for the adsorptive removal of cationic methylene blue (MB) dye from wastewater. The detailed information on the BET surface area, point of zero charge, operational conditions, and results on isotherm, kinetic and thermodynamics as reported on different magsorbents have been compiled. The present paper was planned with the prime objective to make the scientists up-to-date and to provide the valuable information of the developments that have been made as yet for the elimination of MB dye from aqueous solution by employing a variety of magsorbents.〈/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-S030488531933063X-ga1.jpg" width="261" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Pawandeep Kaur, S. Bindra Narang, Shalini Bahel〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research, electromagnetic and microwave absorption properties of the hexagonal ferrites with chemical composition, Sr〈sub〉0.85〈/sub〉La〈sub〉0.15〈/sub〉(CoZr)〈sub〉x〈/sub〉Fe〈sub〉12-2x〈/sub〉O〈sub〉19〈/sub〉 (x = 0.00, 0.25, 0.50, 0.75 and 1.00) were studied in the K-band (18 – 26.5 GHz) and Ka-band (26.5 – 40 GHz) frequency range. Minimum reflection loss (RL) was successfully optimized in the studied frequency range by tuning sample thickness using quarter-wavelength criterion. Absorption results of synthesized hexagonal ferrites show minimum RL in the range of -18.15 dB to -28.69 dB and absorption bandwidth (-10 dB) in the range of 1.04 GHz to 5.87 GHz. The microwave absorption significantly improved with absorption bandwidth (-10 dB) of 5.87 GHz for the composition x = 1.00 at a sample thickness of 2.2 mm. These newly synthesized ferrites have high potential as microwave absorbing material for military applications such as camouflaging of the target and also as EMI (Electromagnetic Interference) suppressor.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 18 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Gang Yin, Ping Li, Zhi Wei, Gang Liu, Zhenhua Yang, Li Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on the virtue of complete isotropy around a dipole source, the normalized source strength (NSS) is introduced to the scalar triangulation and ranging (STAR) method to replace the original tensor contraction and a new real-time magnetic dipole localization method without asphericity error is proposed in this paper. Firstly, three unknown parameters of bearing vector are estimated by solving the equations about the NSS of six faces of the magnetometer cube. Secondly, the magnitude of magnetic moment vector is estimated using NSS and magnitude of the estimated bearing vector. Thirdly, linear equations about three unknown parameters of unit magnetic moment vector are established using the intermediate eigenvalues and NSS of six faces of the cube, and the least square solution is given. Simulations without and with measurement noises have been done to evaluate the performance of the proposed method. The results show that the proposed algorithm is correct in theory and the estimation results are more accurate than two other improved STAR methods.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): M. Zdunek, A. Trzaskowska, J.W. Kłos, N.K.P. Babu, S. Mielcarek〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dispersion relations of surface acoustic waves and spin waves propagating in magnetic [Ni〈sub〉80〈/sub〉Fe〈sub〉20〈/sub〉/Au/Co/Au]〈sub〉10〈/sub〉 multilayers deposited on a silicon substrate have been investigated by high-resolution Brillouin spectroscopy. We measured the spectra of spin waves for two canonical geometries where the spin waves propagate with the wave vector oriented parallel and perpendicular to the direction of static magnetization in-plane magnetized Py layer. We investigated experimentally the crossing of phononic and magnonic dispersion relations and discussed the mechanism of magnetoelastic interaction in this system.〈/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-S0304885319328525-ga1.jpg" width="464" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Jinho Lim, Wonbae Bang, Jonathan Trossman, C.C. Tsai, John B. Ketterson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Using parametric excitation, we have studied the minimum frequency associated with the backward volume (BV) spin wave branch in a thin film of the ferrimagnetic material yttrium iron garnet (YIG) for the magnetic field lying in plane and parallel to the wave vector as well as for out-of-plane field angles. We find that there is a drastic change in the efficiency of parametric excitation between two different pumping frequency regimes.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): B. Kocsis, I. Fekete, L.K. Varga〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this present study, soft magnetic composite samples were made from iron-silicon alloys. For the purpose of optimizing 3D printing parameters, preliminary experiments were performed. Metallographic and computed tomography investigations were used to determine the appropriate sintering settings. Besides the microscopic and CT analysis, considering the permeability spectra have been compared to the samples.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): F. Guillou, D. Paudyal, Y. Mudryk, A.K. Pathak, V. Smetana, A.-V. Mudring, V.K. Pecharsky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rare-earth anti-perovskites with oxygen are an interesting magnetic materials family at the boundary between intermetallics and oxides, they however remain largely unexplored. Here, magnetic and heat capacity investigations, as well as density functional theory (DFT) calculations, were carried out on SnOEu〈sub〉3〈/sub〉. At low magnetic field (〈em〉B〈/em〉 ≤ 0.5 T), a Néel temperature separates antiferromagnetic and paramagnetic phases at 31 K. When applying higher magnetic field below the Néel temperature, successive transformations toward a ferromagnetic state 〈em〉via〈/em〉 a number of intermediate canted magnetic structures are observed and are associated with only modest latent heat and transition entropy. High-pressure magnetic measurements confirm the stable divalent state of Eu up to 1.05 GPa. A direct magnetocaloric effect progressively increases with applied magnetic field above the Néel temperature, reaching −16 J kg〈sup〉–1〈/sup〉 K〈sup〉−1〈/sup〉 for Δ〈em〉B〈/em〉 = 7 T. On the other hand, the inverse magnetocaloric effect of the field-induced transition below 〈em〉T〈/em〉〈sub〉N〈/sub〉 saturates at ~+5 J kg〈sup〉−1〈/sup〉 K〈sup〉−1〈/sup〉. DFT calculations support magnetic instabilities observed experimentally in SnOEu〈sub〉3〈/sub〉 and reveal an unusual exchange mechanism and band topology near the Fermi level.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): M.J. Jiménez, G. Cabeza, J.E. Gómez, D. Velázquez Rodriguez, L. Leiva, J. Milano, A. Butera〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉We have investigated the effects of applying an electric field on the dc and ac magnetic response of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si29.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Fe〈/mi〉〈/mrow〉〈mrow〉〈mn〉89〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si30.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ga〈/mi〉〈/mrow〉〈mrow〉〈mn〉11〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 thin films (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si31.svg"〉〈mrow〉〈mi〉t〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉6〈/mn〉〈/mrow〉〈/math〉, 11, 17, 22, and 28 nm) that have been deposited on ferroelectric PMN-PT (011) and (001) single crystals.〈/p〉 〈p〉Upon the application of an electric field we have observed that 〈em〉M〈/em〉 vs. 〈em〉H〈/em〉 hysteresis loops are modified in films grown on (011) crystals, consistent with a positive magnetostriction constant that depends on film thickness.〈/p〉 〈p〉From ferromagnetic resonance experiments at 9.5 GHz we obtained a thickness dependent magnetoelectric coefficient in the case of (011) substrates, showing a maximum 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si32.svg"〉〈mrow〉〈mi mathvariant="italic"〉dH〈/mi〉〈mo〉/〈/mo〉〈mi mathvariant="italic"〉dE〈/mi〉〈mo〉∼〈/mo〉〈mn〉150〈/mn〉〈/mrow〉〈/math〉 Oe.m/MV for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si33.svg"〉〈mrow〉〈mi〉t〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉28〈/mn〉〈/mrow〉〈/math〉 nm, coincident with the estimations made from 〈em〉M〈/em〉 vs. 〈em〉H〈/em〉 loops.〈/p〉 〈p〉It was found that the direction of easy magnetization could be rotated by 90〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si34.svg"〉〈mrow〉〈mi〉°〈/mi〉〈/mrow〉〈/math〉 upon the application of an electric field only in the case of 28 nm films deposited on PMN-PT (011). In thinner films the magnetoelectric coefficient is too small to overcome the magnetic anisotropy.〈/p〉 〈p〉These results indicate that if magnetostrictive materials are to be applied in straintronic devices the dependence of magnetic parameters with film thickness must be taken in account for optimum performance.〈/p〉 〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Xuan Zhou, Jiasheng Zhang, Xuefeng Liao, Jiayi He, Kaili Li, Zhongwu Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Co-Zr alloys with Si and B modifications show potential for rare earth-free permanent magnets. In this work, Cr was employed for improving the hard magnetic properties of melt-spun Co〈sub〉78-x〈/sub〉Zr〈sub〉16〈/sub〉Cr〈sub〉x〈/sub〉Si〈sub〉3〈/sub〉B〈sub〉3〈/sub〉 (x = 0, 1, 2, 3, and 4) alloys. Their phase constitution, microstructure, and properties have been investigated. The results show that Cr addition can suppress the formation of the soft magnetic FCC-Co phase. The coercivity increased almost linearly with increasing Cr addition, accompanied by decreasing remanence. A high coercivity of 7.7 kOe was obtained in the alloy with 4 at.% Cr substitution for Co, manifesting a 67% coercivity enhancement from 4.6 kOe of the Cr-free alloy. Cr atoms were found to partially substitute Co atoms in the Co-Zr-Cr-Si-B alloys. The size of nanograin decreased with Cr addition alloys, partly due to the precipitation of the secondary Cr phase. After Cr addition, the enhanced positive peak in Henkel plots and the closed recoil loop indicate the improved exchange coupling and consistent magnetic reversal. The alloys with x = 0 and 4 exhibited much lower absolute values of coercivity temperature coefficient, 0.183%/℃ and 0.251%/℃, respectively, and one or two orders of magnitude smaller corrosion current density than that of melt-spun Nd-Fe-B alloys, demonstrating that Co-Zr based alloys have not only excellent thermal stability but also good corrosion resistance. In addition, Cr substitution can further reduce the corrosion rate of Co-Zr alloys in the 3.5 wt% NaCl solution.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): H. Yamasaki, T. Kishimoto, T. Tazawa, H. Yamaguchi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A Bubble’s behavior in a magnetic fluid is one of the most critical issues in understanding the characteristics of the gaseous-liquid two-phase flow in basic fluid science. In this study, to understand the dynamic behavior of a gas bubble in a magnetic fluid, a bubble detached from a single orifice in a magnetic fluid is investigated using a near-infrared light source with a long wavelength of 800–1000 nm. The surface tension of a magnetic fluid, which is a crucial factor in determining the bubble’s characteristics, is also investigated by the maximum bubble pressure method. Based on the visualization measured, it is found that the bubble diameter decreases by applying magnetic field. This is caused by a magnetic body force, that enlarges the bubble in the same direction as the buoyancy force. The measurement of the surface tension of the magnetic fluid shows that the surface tension increases as the applied magnetic field increases. From the measurement of the bubble dynamics, the volume of the detached bubble under a magnetic flux density can be evaluated by a force balance equation with an average error of 16.8%.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): W. Akbar, T. Liaqat, I. Elahi, M. Zulfiqar, S. Nazir〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉By using 〈em〉ab initio〈/em〉 calculations, we explored the electronic and magnetic properties of 3〈em〉d〈/em〉 transition metals (TM = V, Cr, Mn, Fe, Co, Ni, and Cu)-doped 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si12.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉SrTiO〈/mi〉〈/mrow〉〈mrow〉〈mn〉3〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (STO) systems. The stability of doped systems is analyzed by computing their formation energies, which exhibits a strong interdependence on the dopants atomic numbers. Our results show that the versatile electronic and magnetic properties can be obtained by TM-doping, which are ranging from ferromagnetic half-metal (V-, Cr-, and Fe-doped systems), magnetic/non-magnetic semiconductors (Mn-, Co-/Ni-doped systems), and magnetic metal (Cu-doped system). From total and orbital resolved partial density of states, it is found that 3〈em〉d〈/em〉 orbitals of dopant atoms are playing the key role in tunning the physical properties of the STO. The induced magnetism in these doped systems is explained by comparing the valence electronic configurations of host (Ti) and doped (TM) atoms. Our findings may trigger further experimental researches to obtain stable magnetic properties in TM-doped STO systems.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Martin Magnuson, Maurizio Mattesini〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetism in the inherently nanolaminated ternary MAX-phase Cr〈sub〉2〈/sub〉GeC is investigated by element-selective, polarization and temperature-dependent, soft X-ray absorption spectroscopy and X-ray magnetic circular dichroism. The measurements indicate an antiferro-magnetic Cr-Cr coupling along the 〈em〉c〈/em〉-axis of the hexagonal structure modulated by a ferromagnetic ordering in the nanolaminated 〈em〉ab〈/em〉-basal planes. The weak chromium magnetic moments are an order of magnitude stronger in the nanolaminated planes than along the vertical axis. Theoretically, a small but notable, non-spin-collinear component explains the existence of a non-perfect spin compensation along the 〈em〉c〈/em〉-axis. As shown in this work, this spin distortion generates an overall residual spin moment inside the unit cell resembling that of a ferri-magnet. Due to the different competing magnetic interactions, electron correlations and temperature effects both need to be considered to achieve a correct theoretical description of the Cr〈sub〉2〈/sub〉GeC magnetic properties.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): José F.M.L. Mariano, Valentim G. Bessergenev, João P. Lourenço, Martin Hantusch, Eberhard Burkel, Ana M. Botelho do Rego, Michal Rajňák, Milan Timko, Peter Kopčanský〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work reports on the structural and magnetic properties of TiO〈sub〉2〈/sub〉 P25 Degussa powder doped with cobalt. Dissolution of cobalt in TiO〈sub〉2〈/sub〉 matrix was achieved by precipitation of tris(diethyldithiocarbamato) cobalt(III) (CoDtc - Co[S〈sub〉2〈/sub〉CN(C〈sub〉2〈/sub〉H〈sub〉5〈/sub〉)〈sub〉2〈/sub〉]〈sub〉3〈/sub〉 in chloroform (CHCl〈sub〉3〈/sub〉) and consequent thermal treatment. Five different Co atomic percentage contents were chosen, e.g., 0.5%, 1%, 2%, 5% and 10%. It was shown that cobalt atoms are uniformly distributed across TiO〈sub〉2〈/sub〉 matrix and exhibit antiferromagnetic interactions at low temperatures.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Lokesh Saini, Manoj Kumar Patra, Ambesh Dixit〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We designed an experimental set-up and optimized the process parameters for large scale synthesis (250 g) of low density nickel core metal with graphitic carbon shell as functional nanomaterial with highly reproducible physical properties. Structural characterization reveals formation of nano-core FCC Ni metal ~40 nm with ~7 nm thick graphitic shell after annealing at 850 °C. Room temperature field dependent magnetic (M−H) measurement reveals significant saturation magnetization in the sample even with non-magnetic graphite shell. The structural and magnetic properties are compared with small-scale batch synthesis (10 g), reported earlier. The temperature-dependent magnetic measurements suggest that Ni/graphite core-shell samples, annealed at 550 °C, and 700 °C are superparamagnetic, whereas sample annealed at 850 °C is ferromagnetic. The developed synthesis set-up is simple, environment friendly, and cost-effective. Further, to cater the end use applications of such materials for industrial, bio-medical and microwave absorption, the reported method may be further scaled up for large production.〈/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-S0304885319336637-ga1.jpg" width="286" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Fariborz Kargar, Michael Balinskiy, Howard Chiang, Andres C. Chavez, John Nance, Alexander Khitun, Gregory P. Carman, Alexander A. Balandin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report the results of micro-Brillouin-Mandelstam light scattering spectroscopy of thermal magnons in the two-phase synthetic multiferroic structure consisting of a piezoelectric [Pb(Mg〈sub〉1/3〈/sub〉Nb〈sub〉2/3〈/sub〉)O〈sub〉3〈/sub〉]〈sub〉(1−x)〈/sub〉–[PbTiO〈sub〉3〈/sub〉]〈sub〉x〈/sub〉 (PMN-PT) substrate and a Ni thin film. The experimental data reveal the first two modes of the perpendicular standing spin waves (PSSW) spatially confined across the Ni thin film. A theoretical analysis of the frequency dependence of the PSSW peaks on the external magnetic field reveals the asymmetric boundary condition, 〈em〉i.e.〈/em〉 pinning, for variable magnetization at different surfaces of the Ni thin film. The strain field induced by applying DC voltage to PMN-PT substrate leads to a downshift of PSSW mode frequency owing to the magneto-elastic effect in Ni, and corresponding changes in the spin-wave resonance conditions. The observed non-monotonic dependence of the PSSW frequency on DC voltage is related to an abrupt change of the pinning parameter at certain values of the voltage. The obtained results are important for understanding the thermal magnon spectrum in ferromagnetic films and the development of the low-power spin-wave devices and quantum sensors.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): H. Verma, T. Mekuria, P. Seck, H. Hong, S.P. Karna, D. Seifu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The saturation magnetization of composites of carbon nanotubes and CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 (CFO) magnetic nanoparticles synthesized through a novel one-step process in the presence of a surfactant (sodium dodecyl-benzene-sulfonate) show significant increase, to 208 emu/g. This value of saturation magnetization of the composite is a factor of 3.3 higher than pristine CFO nanoparticles. This is the first time such a remarkable magnetic behavior of CFO/ carbon nanotubes composite is presented. The increased magnetism is attributed to the proximity effect between uniformly distributed ferromagnetic CFO nanoparticles on the surface of carbon nanotubes and hybridization of the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉π〈/mi〉〈/mrow〉〈/math〉-electronic states of carbon and the 3d-bands of CFO. Scanning electron microscopy images confirm uniform and dense distribution of CFO nanoparticles on carbon nanotubes. Magnetic force microscopy images confirm the formation of uniformly distributed magnetic stripe domains. The sample was characterized at ambient using X-ray diffraction, Raman Spectroscopy, atomic force microscopy, scanning electron microscopy, scanning transmission electron microscopy, and high-resolution transmission electron microscopy. Magnetic properties were characterized by magnetic force microscopy and magnetometry using vibrating sample magnetometer.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): A.V. Nagornyi, V. Socoliuc, V.I. Petrenko, L. Almasy, O.I. Ivankov, M.V. Avdeev, L.A. Bulavin, L. Vekas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Structure characterizations of concentrated water-based magnetic fluids stabilized by oleic and lauric acids were done by means of small-angle neutron scattering (SANS) and complemented by dynamic light scattering and magnetization analysis. Stability of ferrofluids with time against sedimentation was concluded despite the presence of aggregates in solutions. Differences in the average sizes of individual polydisperse magnetite nanoparticles coated with surfactants and their aggregates were revealed. Structural parameters obtained from SANS have been confirmed by magnetogranulometry data. The comparative analysis of the aggregation and its change upon dilution is made basing on the data of SANS and dynamic light scattering techniques.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): A.B. Dobroserdova, P.A. Sánchez, V.E. Shapochkin, D.A. Smagin, V.S. Zverev, S. Odenbach, S.S. Kantorovich〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉FORCs (first-order reversal curves) diagrams prove to be an efficient experimental technique to investigate magnetic interactions in complex systems. In experiments, as a rule, it is difficult to relate actual microstructural changes to the evolution of FORCs diagrams. Here, using Molecular Dynamics simulations, we calculate FORCs for two simple models of a magnetic elastomer. The simplicity of these models allows to relate directly both, the rigidity of the matrix and the magnetoelastic coupling to the shape and intensity of FORCs diagrams.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): U. Ahmed, U. Aydin, M. Zucca, S. Palumbo, R. Kouhia, P. Rasilo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents the implementation of magneto-mechanical constitutive law utilizing thermodynamic approach in a 3D finite element solver using COMSOL Multiphysics software. The analytical expression for the magnetic field strength and stress is derived from the constitutive model utilizing magnetic flux density and mechanical strain as state variables. The constitutive model is successfully implemented in commercially available software COMSOL. This implementation allows 3D analysis of an energy harvester device efficiently and accurately. A prototype concept device is developed to validate the model and its implementation. The device is tested under uniaxial compressive loading by varying the preload, dynamic load and magnetic bias. The model is validated by comparing the simulated and experimental results. The comparison shows that the model can reasonably predict the optimal value of the preload and magnetic bias yielding maximum power and is able to follow the measurement trends. This model can be used as a suitable tool to analyze the behavior of the concept energy harvesters and determine the optimal design parameters.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): S. Nandi, Y.M. Jana, D. Chakraborty, J. Alam, P. Bag, S.S. Islam, R. Nath〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The pyrochlore, Gd〈sub〉2〈/sub〉FeSbO〈sub〉7〈/sub〉, having general formula unit 〈em〉A〈/em〉〈sub〉2〈/sub〉〈em〉B〈/em〉〈sub〉2〈/sub〉O〈sub〉7〈/sub〉, was chosen for magnetic and heat capacity study in this work due to presence of Fe〈sup〉3+〈/sup〉 moments, whose 〈em〉3d〈/em〉 orbitals (3〈em〉d〈/em〉〈sup〉5〈/sup〉:〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mn〉3〈/mn〉〈msubsup〉〈mi〉t〈/mi〉〈mrow〉〈mn〉2〈/mn〉〈mi〉g〈/mi〉〈/mrow〉〈mn〉3〈/mn〉〈/msubsup〉〈msubsup〉〈mi〉e〈/mi〉〈mi〉g〈/mi〉〈mn〉2〈/mn〉〈/msubsup〉〈/mrow〉〈/math〉) are half-filled and carry a large magnetic moment, at 〈em〉B〈/em〉 site of the structure, and hence create additional Gd−O−Fe−O−Gd pathways, which result in strongly antiferromagnetic superexchange interactions among the Gd−Gd spins as well as for the Gd−Fe bonds. Gd〈sub〉2〈/sub〉FeSbO〈sub〉7〈/sub〉 behaves paramagnetic down to ~10 K with effective antiferromagnetic nearest-neighbour interactions resulting negative Curie-Weiss temperature, 〈em〉θ〈/em〉〈sub〉CW〈/sub〉 = −12.62 K. Fe sublattice exhibits a weak ferromagnetic transition at 〈em〉T〈sub〉C〈/sub〉〈/em〉 ≈ 5 K. The frustration index 〈em〉f〈/em〉 = |〈em〉θ〈/em〉〈sub〉CW〈/sub〉|/〈em〉T〈sub〉C〈/sub〉〈/em〉 becomes 2.5 indicative of moderate frustration, which may prevent Palmer-Chalker ground state configuration of Gd sublattice at lower temperature in the system. Heat capacity 〈em〉C〈sub〉p〈/sub〉〈/em〉 exhibits a broad anomaly at ~3.1 K and calculated magnetic heat capacity 〈em〉C〈sub〉m〈/sub〉〈/em〉/〈em〉T〈/em〉 attains a peak at ~1 K, but is much weaker than for other pyrochlores Gd〈sub〉2〈/sub〉〈em〉B〈/em〉〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 (〈em〉B〈/em〉 = Sn, Ti, Ge, Pt) which are all found to order at 1 K or lower, thereby reflecting a short-range second-order transition in Gd〈sub〉2〈/sub〉FeSbO〈sub〉7〈/sub〉. The nature of transition was also verified by Arrott plot of magnetization. Finally the magneto-thermodynamic data were analyzed on the basis of a cooperative two-sublattice model taking account of intra-sublattice (Gd−Gd and Fe−Fe) and inter-sublattice (Gd−Fe) magnetic interactions, defined by three molecular-field parameters, 〈em〉λ〈/em〉〈sub〉Gd−Gd〈/sub〉 = −0.71 T/〈em〉μ〈/em〉〈sub〉B〈/sub〉, 〈em〉λ〈/em〉〈sub〉Fe−Fe〈/sub〉 = 0.87 T/〈em〉μ〈/em〉〈sub〉B〈/sub〉, and 〈em〉λ〈/em〉〈sub〉Gd−Fe〈/sub〉 = −0.61 T/〈em〉μ〈/em〉〈sub〉B〈/sub〉 in presence of the easy-planer crystal-field anisotropy at Gd-site. Without Gd−Fe interaction, two 〈em〉independent〈/em〉 interpenetrating Gd〈sup〉3+〈/sup〉 and Fe〈sup〉3+〈/sup〉Sb〈sup〉5+〈/sup〉 sublattices can not precisely demonstrate the measured thermomagnetic properties of Gd〈sub〉2〈/sub〉FeSbO〈sub〉7〈/sub〉. This study thus revealed that 3〈em〉d〈/em〉−4〈em〉f〈/em〉 magnetic interactions offer Gd〈sub〉2〈/sub〉FeSbO〈sub〉7〈/sub〉 a unique place in the series of gadolinium-based pyrochlores.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): B. Abraime, K. El Maalam, L. Fkhar, A. Mahmoud, F. Boschini, M. Ait Tamerd, A. Benyoussef, M. Hamedoun, E.K. Hlil, M. Ait Ali, A. El Kenz, O. Mounkachi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cobalt ferrite nanopowders were prepared with low annealing temperatures (400 °C and 600 °C) using four different synthesis methods: co-precipitation, sol-gel, sol-gel autocombustion and microemulsion. The pure phase is obtained in all the samples and confirmed using the XRD diffraction. The crystallite size is calculated based on the XRD patterns and ranged between ~9 nm and ~26 nm. The SEM micrographs show an agglomeration with an increase of grain size between 400 °C and 600 °C samples for all the used methods. The magnetic properties are given. The best obtained values are M〈sub〉S〈/sub〉 = 80,319 emu/g, H〈sub〉C〈/sub〉 = 2057,97 Oe and (BH)〈sub〉max〈/sub〉 = 0.3313 MGOe for co-precipitation, sol-gel and sol-gel autocombustion, respectively. An improvement of 89% in (BH)〈sub〉max〈/sub〉 value is observed in the case of sol-gel auto-combustion when we go from 400 °C to 600 °C.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Nikolay Kalanda, Marta Yarmolich, Alexander Petrov, Igor Raevski, Stanislav Kubrin, Svetlana Raevskaya, Ivan Bobrikov, Andrei Lazavenka, Dong-Hyun Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sr〈sub〉2〈/sub〉FeMoO〈sub〉6–〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉 polycrystalline samples with different oxygen content (6−〈em〉x〈/em〉) and various degrees of superstructural ordering of Fe/Mo cations (〈em〉P〈/em〉) were obtained by the solid-phase method from the SrFeO〈sub〉2.52〈/sub〉 and SrMoO〈sub〉4〈/sub〉 precursors. From the investigation on the influence of oxygen non-stoichiometry and the 〈em〉P〈/em〉 parameter on the magnetic properties of Sr〈sub〉2〈/sub〉FeMoO〈sub〉6–〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉, it was found that with an increase in 〈em〉P〈/em〉 and a decrease in the (6−〈em〉x〈/em〉) value from 5.99 to 5.94, an increase in the magnetization values is observed in the temperature range 77–600 K. For all the Sr〈sub〉2〈/sub〉FeMoO〈sub〉6–〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉 samples there is a tendency that 〈em〉P〈/em〉 value rises with increasing 〈em〉x〈/em〉, where, accordingly, the volume fraction of regions in which there are no anti-structural defects increases as well. This is also indicated by Mössbauer spectroscopy data, confirming an increase in the area of the S1 sextet corresponding to Fe ions in highly ordered regions and a decrease in the area of the S2 sextet associated with disordered regions. Using the temperature scanning method, the temperatures of the onset and completion of the transition from the paramagnetic to the ferrimagnetic state and, correspondingly, the blurring width of the transition have been estimated. It turned out that with decreasing 〈em〉P〈/em〉, the blurring of the transition increases, which is associated with an increase in the concentration of anti-structural defects.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Oksana Petrichenko, Guntars Kitenbergs, Martins Brics, Emmanuelle Dubois, Régine Perzynski, Andrejs Cēbers〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Energy input by under-field rotation of particles drives the systems to emergent non-equilibrium states. Here we investigate the suspension of rotating magnetic cubes. Micron-sized hematite cubes are synthesized and observed microscopically. When exposed to a rotating magnetic field, they form rotating swarms that interact with each other like liquid droplets. We describe the swarming behaviour and its limits and characterize the swarm size and angular velocity dependence on the magnetic field strength and frequency. A quantitative agreement with a theoretical model is found for the angular velocity of swarms as a function of the field frequency.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 15 April 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 500〈/p〉 〈p〉Author(s): Yu.N. Starodubtsev, V.S. Tsepelev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic losses in the Fe〈sub〉72,5〈/sub〉Cu〈sub〉1〈/sub〉Nb〈sub〉2〈/sub〉Mo〈sub〉1,5〈/sub〉Si〈sub〉14〈/sub〉B〈sub〉9〈/sub〉 nanocrystalline alloy were investigated in a wide range of magnetic induction from 0.01 to 1.0 T and frequencies from 60 Hz to 100 kHz. Dependences of magnetic losses approximated by power function. It is shown that the exponent of the power function depends on the ratio of hysteresis losses and eddy current losses, as well as on the number of actively moving domain walls. The number of domain walls was calculated using a domain model and measured eddy current losses.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): William Salazar, Luis Carlos Moreno-Aldana, John William Sandino del Busto〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic domain structure of Sr〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉Z hexaferrite related to crystal orientation is investigated by Lorentz microscopy and electron holography. The sample of Sr〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉Z, prepared by citrate method, was milled in two different crystallographic orientations by focused ion beam. One of them was prepared with its 〈em〉c〈/em〉 crystallographic axis direction parallel to the electron beam at the TEM, and the other one, perpendicular to this direction. In both specimens, Lorentz micrographs revealed some structure domain walls e.g. stripes and magnetic flux-closure. Furthermore, phase micrographs acquired by electron holography revealed magnetic domain structures with 145.3° ± 5.2° domain walls.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 1 May 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 501〈/p〉 〈p〉Author(s): Peter Bury, František Černobila, Marek Veveričík, Jozef Kúdelčík, Štefan Hardoň, Michal Rajňák, Katarína Pavlovičová, Milan Timko, Peter Kopčanský〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Surface acoustic waves (SAWs) are used for the first time to investigate structural changes in transformer oil-based magnetic fluids under magnetic field. The measurement of the attenuation of SAW propagating along the interface between magnetic fluid and the piezoelectric substrate is showed as an effective tool to study such processes in the case of magnetic fluids when the obviously utilized longitudinal acoustic waves due to the higher viscosity are not available. The magnetic particles FeO.Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 in several different volume concentrations, from 0.05% to 3.5%, were added to the transformer oil MOL. Both linear increasing and jumped changed magnetic field were applied to study structural changes. The interaction between the magnetic field and magnetic moments of nanoparticles can lead to the aggregation of magnetic nanoparticles and following chain or cluster formations that have an influence on the SAW attenuation. The concentration of magnetic nanoparticles and temperature of magnetic fluid have a decisive influence on structural changes due to the changes of viscosity and thermal motion with the increasing temperature that both affect the process of cluster formation. The measurement of the acoustic anisotropy and applying the theoretical predictions gives additional useful information about the structure of nanoparticles formations in investigated magnetic fluids. Obtained results are compared and discussed.〈/p〉〈/div〉 〈/div〉