ALBERT

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): Ram Kumar, Jyoti Sharma, Kartik K. Iyer, E.V. Sampathkumaran〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report temperature (〈em〉T〈/em〉) dependence (2–300 K) of DC and AC magnetization (〈em〉M〈/em〉), isothermal remnant magnetization (〈em〉M〈sub〉IRM〈/sub〉〈/em〉), heat-capacity (〈em〉C〈/em〉), electrical resistivity (ρ), and magnetoresistance (MR) of a ternary intermetallic compound, Gd〈sub〉4〈/sub〉PtAl, crystallizing in a cubic (space group 〈em〉F〈/em〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mover〉〈mn〉4〈/mn〉〈mo〉-〈/mo〉〈/mover〉〈/mrow〉〈/math〉3〈em〉m〈/em〉) structure. In this structure, there are three sites for the rare-earth. The magnetization data reveal that, in addition to a magnetic transition at 64 K, there is another magnetic feature below 20 K. The 〈em〉C〈/em〉(〈em〉T〈/em〉) data reveal an upturn below 64 K, shifting to a lower temperature with increasing field, which establishes that the onset of magnetic order is of an antiferromagnetic type. However, there is no worthwhile feature near 20 K in the 〈em〉C(T)〈/em〉 curve. Ac susceptibility peak undergoes an observable change with frequency and, in particular the peak around 20 K gets suppressed with the application of a dc magnetic field; in addition, 〈em〉M〈sub〉IRM〈/sub〉〈/em〉 undergoes a slow decay with time and isothermal 〈em〉M〈/em〉 exhibits low-field hysteresis below 20 K only, which are typical of spin-glasses. The results overall suggest that this compound is a reentrant spin-glass in zero field. There are experimental signatures pointing to the existence of both antiferromagnetic and ferromagnetic components, competing with the variation of temperature and magnetic field, as a result of which electrical and magnetoresistance behaviors are peculiar. The results overall suggest that this compound exhibits interesting magnetic and transport properties.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): N. Leuning, S. Steentjes, M. Heller, S. Korte-Kerzel, K. Hameyer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In material models for the finite-element simulation of electrical machines and the preceding magnetic measurements, the magnetic anisotropy of non-grain oriented electrical steel is usually considered in an oversimplified way, if at all. The magnetization behavior between rolling and transverse direction is not linear and varies with magnetic polarization, a relation that comes in addition to the complexity of the effect. In this paper, the magnetization anisotropy of five industrial non-grain oriented electrical steels is measured with a 1-D single-sheet-tester. The results are evaluated and correlated to the crystallographic texture of the studied materials. An approach to model magnetization curves at 50 Hz in arbitrary directions of the sheet plane is presented. The model is parametrized by measured magnetization curves along three different spatial directions and by macro-texture data in form of an orientation distribution function. This approach leads to a model that replicates the crossing of magnetization curves of different orientations with adequate quantitative accuracy for the application in FE magnetic field simulations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): E. Saavedra, J. Escrig, J.L. Palma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetization reversal process of interconnected pentagonal spin ice systems was investigated using micromagnetic simulations and experimental measurements. Five different systems were investigated, beginning with the interconnected Shakti lattice and introducing deformations with the idea of obtaining pentagonal tiling (belonging to the P4 group) until reaching an interconnected square lattice. In all pentagonal lattices, ferromagnetic domains are pinned, acting as isolated domains in an antiferromagnetic lattice, with Cairo tiling being the lattice that allows pinning more domains. Experimental measurements on a Cairo lattice of larger dimensions show that the shape of the hysteresis curve is invariant to the size of the bars that make up the interconnected pentagonal spin ice systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): H.X. Zeng, Q.X. Wang, J.S. Zhang, X.F. Liao, X.C. Zhong, H.Y. Yu, Z.W. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Different from many previous reports, La-Al-Cu alloys with different Al/Cu ratios containing only high abundant rare earth element La were employed for grain boundary diffusion treatment for sintered NdFeB permanent magnets. It is found that Al and Cu contents should be optimized to achieve coercivity enhancement. The coercivity of the magnet was enhanced from 1000 to 1006, 1077 and 1156 kA/m after La〈sub〉70〈/sub〉Al〈sub〉10〈/sub〉Cu〈sub〉20〈/sub〉, La〈sub〉70〈/sub〉Al〈sub〉15〈/sub〉Cu〈sub〉15〈/sub〉 and La〈sub〉70〈/sub〉Al〈sub〉20〈/sub〉Cu〈sub〉10〈/sub〉 alloys diffusion, at 800 °C for 1 h followed by 500 °C for 3 h. The coercivity stability was also improved, indicated by the enhanced temperature coefficient of β from −0.63 to −0.61, −0.61 and −0.60%/K. Microstructure investigation indicates that the formation of continuous grain boundary phase after diffusion reduces the magnetic exchange interaction and contributes to the enhanced coercivity. After diffusion, the La〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 phase was observed in both the triple junction and strip grain boundary. La, Al and Cu elements showed different distributions in the magnets. The diffusion coefficients obtained from Fick’s second law indicate that La diffuses faster than Al and Cu at 800 °C, which explains the various effects of the diffusion sources and different coercivity enhancements by the alloys with different Al/Cu ratios. Although the process should be further optimized, the current results demonstrate that the grain boundary diffusion using low cost La-Al-Cu alloys can improve the microstructure and enhance the coercivity of NdFeB magnets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Chang-Wei Wu, Dao-Xin Yao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two-dimensional (2D) ferromagnetic semiconductors with robust magnetism are urgently desired for nanoscale spintronics applications. However, it remains a challenge to realize them experimentally. In this work, we proposed intriguing 2D p-orbital ferromagnetic semiconductors 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si29.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉X〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si30.svg"〉〈mrow〉〈mi〉X〈/mi〉〈mo〉=〈/mo〉〈mi mathvariant="italic"〉Ca〈/mi〉〈mo〉,〈/mo〉〈mi mathvariant="italic"〉Sr〈/mi〉〈/mrow〉〈/math〉) monolayer with 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si31.svg"〉〈mrow〉〈mn〉3〈/mn〉〈msub〉〈mrow〉〈mi〉μ〈/mi〉〈/mrow〉〈mrow〉〈mi〉B〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 magnet per unit under O surface termination using first-principles calculations. The 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si32.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ca〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer is bipolar magnetic material (BMS) with spin-flip gap 0.24 eV, and the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si33.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Sr〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 is half-semiconductor (HSC) with spin-flip gap 0.31 eV, which is large enough to prevent the spin-flip transition. The Curie temperature can reach to 206 and 239 K, respectively, due to the superexchange interaction between 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si34.svg"〉〈mrow〉〈msup〉〈mrow〉〈mi〉N〈/mi〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 ions. The values are much higher than the boiling point of liquid nitrogen (77 K) and comparable to that of the reported 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si35.svg"〉〈mrow〉〈mi mathvariant="normal"〉ScCl〈/mi〉〈/mrow〉〈/math〉 monolayer. Moreover, the half metals are obtained via carrier doping for both the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si36.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ca〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si37.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Sr〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayers. In addition, the half-metallic completely spin-polarized direction of BMS 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si38.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ca〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer can be controlled by carrier doping type. Furthermore, the magnetism of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si39.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉X〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer is derived from p orbital, without the involvement of conventional transition metals or rare earth atoms. This is advantageous for high-speed and long-distance spin-polarization transport. These results suggest that the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si40.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉X〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer can develop spin field effect transistor for information processing and storage, and open opportunities for designing new ferromagnetic semiconductors.〈/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-S0304885319322772-ga1.jpg" width="160" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/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): Chicheng Ma, Kai Liu, Xingqi Han, Sheng Yang, Nan Ye, Jiancheng Tang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The martensitic transformation (MT) and magnetocaloric properties are investigated in melt-spun Mn〈sub〉50〈/sub〉Ni〈sub〉31.5〈/sub〉Co〈sub〉8.5〈/sub〉Ti〈sub〉10〈/sub〉 all-3〈em〉d〈/em〉-metal alloy ribbons fabricated at different wheel speeds (WSs), 15, 20, and 25 m/s. All these ribbon samples reveal a coexistence of the predominant 5-layer modulated (5 M) (monoclinic, space group 〈em〉P〈/em〉2/〈em〉m〈/em〉) martensite and a small amount of non-modulated (NM) 〈em〉L〈/em〉1〈sub〉0〈/sub〉 structure (tetragonal, space group 〈em〉P〈/em〉4/〈em〉mmm〈/em〉) martensite at room temperature (RT), implying the MT temperature is above RT. With the increase of WSs from 15 to 25 m/s, the structural and magnetic parameters, such as average grain size, unit cell volume, MT temperature, and magnetic entropy change, decrease. However, it is worth noting that from 20 to 25 m/s, the reduction becomes much more sluggish or even almost stagnate in comparison with that from 15 to 20 m/s. Large effective refrigeration capacity ~79.4 J kg〈sup〉−1〈/sup〉 is obtained in sample with 20 m/s under 〈em〉μ〈/em〉〈sub〉0〈/sub〉Δ〈em〉H〈/em〉 = 0–5 T, indicating that these ribbons could be the potential candidate for magnetic refrigeration. The origins of manipulation in MT by WSs in these ribbon samples are discussed.〈/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): Xiao Zhou, Ruirui Liu, Haitao Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The microstructures and soft magnetic properties of Co〈sub〉66〈/sub〉Fe〈sub〉4〈/sub〉Mo〈sub〉2〈/sub〉Si〈sub〉16〈/sub〉B〈sub〉12〈/sub〉 amorphous tape wound core were systematically investigated. The phase composition and corresponding structure evaluation of Co〈sub〉66〈/sub〉Fe〈sub〉4〈/sub〉Mo〈sub〉2〈/sub〉Si〈sub〉16〈/sub〉B〈sub〉12〈/sub〉 amorphous ribbon after annealing at various temperatures were identified firstly. In particular, at 758 K the microstructure of the ribbon is primarily composed of Co〈sub〉2〈/sub〉B, Fe〈sub〉2〈/sub〉B and β-Co phases. With the temperature approaching to 768 K, the new phases α-Co and CoSi appears. When the temperature increases to 778 K, the mixed phase combination of α(Co) + β(Co) + Co〈sub〉2〈/sub〉B + Fe〈sub〉2〈/sub〉B + CoSi exists along with an apparent nano-crystallization. The soft magnetic properties of tape wound core assembled by Co〈sub〉66〈/sub〉Fe〈sub〉4〈/sub〉Mo〈sub〉2〈/sub〉Si〈sub〉16〈/sub〉B〈sub〉12〈/sub〉 amorphous ribbon were then studied at annealed temperature from 713 K to 753 K. At 723 K, we found the permeability is highest with a maximum value of 〈em〉μ〈sub〉m〈/sub〉〈/em〉 = 1.675 × 10〈sup〉3〈/sup〉, and the coercive force is lowest with a minimum value of 0.134 Oe. The magnetization curve and the hysteresis loop of established tape would core annealed at 713–753 K remain almost unchanged. Finally, the relation between frequency and magnetic permeability and quality factor were carefully examined at different annealing temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Rihab Jabbar, Sabah H. Sabeeh, Awham M. Hameed〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Manganese (Mn〈sup〉+2〈/sup〉) doped spinel cobalt ferrites nanoparticles (NPs) having composition (Mn〈sub〉x〈/sub〉Co〈sub〉1-x〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 where x = 0.2, 0.4, 0.6 and 0.8) were synthesized by sol-gel precipitation method. The structural, dielectric and magnetic properties were characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), LCR meter, and vibrating sample magnetometer (VSM). The average crystallite size (D) was found to increase from 10.79 nm to 14.18 nm with increasing the Mn〈sup〉+2〈/sup〉 doping ratio from (0.2 to 0.6) then decrease to 9.95 nm with further increasing of Mn〈sup〉+2〈/sup〉 to (0.8). FTIR spectrum confirmed the formation of the spinal structure of ferrite, where the main observed bands (416.64 – 459.07 cm〈sup〉-1〈/sup〉) assigned to the octahedral complexes and (513.08 – 574.81 cm〈sup〉-1〈/sup〉) assigned to tetrahedral complexes. The dielectric properties of samples found to be decreased with increasing the doping ratio. While the hysteresis loop obtains from VSM indicated the formation of soft magnetic material and the saturation magnetization decrease from 56 emu g〈sup〉-1〈/sup〉 (Mn〈sup〉+2〈/sup〉 = 0.2) to 38 emu g〈sup〉-1〈/sup〉 (Mn〈sup〉+2〈/sup〉 = 0.8).〈/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): Yanan Zhang, Lu Li, Shunqun Liu, Diangang Pan, Lei Chen, Hong Chang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The nonmagnetic In〈sup〉3+〈/sup〉 doping in the hexagonal SrFe〈sub〉12−〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉In〈em〉〈sub〉x〈/sub〉〈/em〉O〈sub〉19〈/sub〉 (〈em〉x〈/em〉 = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 1 and 2) permanent magnet increases the saturation magnetization at 300 K with the highest value up to 73.87 emu/g at 〈em〉x〈/em〉 = 0.5, and decreases it with 〈em〉x〈/em〉 〉 0.5. The coercive field keeps almost the same for 〈em〉x〈/em〉 ≤ 0.2, but it decreases with 〈em〉x〈/em〉 〉 0.2. The Curie temperature linearly decreases from 740 K for 〈em〉x〈/em〉 = 0 to 610 K for 〈em〉x〈/em〉 = 1.0, and decreases at a much lower rate to 592 K for 〈em〉x〈/em〉 = 2.0. The XPS, FT-IR and UV–vis spectra are carried out to characterize the relations between the magnetic properties and the structure. The In〈sup〉3+〈/sup〉 ions preferentially occupy the tetragonal 4f1 site, deduced from the xrd refinement and the FT-IR spectra. It is consistent with the increasing magnetization by the In〈sup〉3+〈/sup〉 doping. Oxygen vacancies exist in the compounds. The In〈sup〉3+〈/sup〉 doping and oxygen vacancies deteriorate the coercivity, while Fe〈sup〉2+〈/sup〉 ions are in favor of a high magnetocrystalline anisotropy. The energy band gap of SrFe〈sub〉12−〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉In〈em〉〈sub〉x〈/sub〉〈/em〉O〈sub〉19〈/sub〉 increases with the increasing In〈sup〉3+〈/sup〉 doping from 1.75 eV for 〈em〉x〈/em〉 = 0 to 1.87 eV for 〈em〉x〈/em〉 = 1.0, but that of 〈em〉x〈/em〉 = 2.0 decreases to 1.79 eV. It reflects that oxygen vacancies in 〈em〉x〈/em〉 = 2.0 play a function on the energy band gap.〈/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): D.A. Petrov, R.D. Ivantsov, S.M. Zharkov, D.A. Velikanov, M.S. Molokeev, C.-R. Lin, C.-T. Tso, H.-S. Hsu, Y.-T. Tseng, E.-S. Lin, I.S. Edelman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Effect of Ag inclusions on magnetic properties and magnetic circular dichroism (MCD) of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanoparticles (NPs) in the mixed system of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and Ag NPs in dependence on the relative concentration of the components is presented. The samples were synthesized by the thermal decomposition of the mixture of constant concentration of Fe(NO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉·9H〈sub〉2〈/sub〉O and varied concentration of AgNO〈sub〉3〈/sub〉. The synthesized powdered samples consisted of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and Ag NPs located very close with each other, and in the most cases the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs were bordered with the Ag nanocrystals. The Ag introducing in the samples does not effect, practically, in the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs morphology and size distribution. At the same time, Ag NPs in the powdered samples cause a decrease in the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs magnetization and shift of the blocking temperature to lower temperatures, both approximately proportional to the Ag concentration. Most significant changes are revealed in the MCD spectra in the energy region of 1.2–2.2 eV. We have discussed the influence of the Ag NPs on the MCD spectra features in terms of the charge-transfer electron transitions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Sanae Zriouel〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on our works [1], [2], [3], [4], we report the magnetic and hysteretic properties of graphene-based Janus materials namely, pure and doped zigzag graphone nanoribbons, hexagonal core/shell graphene-like nanoribbon, and graphyne core/shell nanoparticle, within the framework of both Monte Carlo calculations and mean field theory. We have reported the effects of the Hamiltonian parameters on the magnetic and the thermodynamic quantities of the systems. The total magnetization, the susceptibility, the specific heat, and the hysteresis curves, as well as the critical temperature and the compensation behavior, that is of crucial importance for technological applications such as thermo-optical recording, are studied. A number of characteristic behaviors are found, such as the existence of two new and non-classified magnetization profiles in addition to the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si80.svg"〉〈mrow〉〈mi〉Q〈/mi〉〈mo〉-〈/mo〉〈mo〉,〈/mo〉〈mi〉P〈/mi〉〈mo〉-〈/mo〉〈/mrow〉〈/math〉, and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si81.svg"〉〈mrow〉〈mi〉N〈/mi〉〈mo〉-〈/mo〉〈/mrow〉〈/math〉types of compensation behavior and the occurrence of square, single, and triple hysteresis loops which exhibit different step effects and various shapes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): M. Zarifi, P. Kameli, T. Raoufi, A. Ghotbi Varzaneh, D. Salazar, M.I. Nouraddini, L. Kotsedi, M. Maaza〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetocaloric properties in La〈sub〉0.5〈/sub〉Ca〈sub〉0.5-x〈/sub〉Pb〈sub〉x〈/sub〉MnO〈sub〉3〈/sub〉 (0≤x≤0.2) manganites are considered by both direct and indirect measurement techniques. The ac susceptibility shows that the compounds with low Pb doping exhibit mixture of CE-type AFM ordering and FM phase, while at high Pb doping FM phase is dominated. For samples x=0 and 0.05, the M-H curves at different temperatures exhibit the magnetization first increases and then decreases with decreasing temperature, indicating the growth of the AFM phase below T〈sub〉N〈/sub〉. In the curves for samples x=0.1 and 0.2, with decreasing temperature the magnetization increases and the FM phase is overcoming at low temperature. The magnetic entropy change (ΔS〈sub〉M〈/sub〉) is enhanced continuously with increasing Pb concentration up to x=0.1, then slightly decreases. The magnetocaloric effect in the vicinity of T〈sub〉C〈/sub〉 for x= 0.1 and 0.2 was investigated by the direct field-induced adiabatic temperature change (ΔT〈sub〉ad〈/sub〉). The results of the direct method show the absolute values of obtained ΔT〈sub〉ad〈/sub〉 are almost the same for both samples (0.62 and 0.53 K under 1.96 T for x=0.1 and 0.2, respectively). The outcomes demonstrate that doping by Pb is a promising material for the magnetic refrigeration.〈/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): Shabir Ahmad Mir, Dinesh C. Gupta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ba〈sub〉2〈/sub〉MUO〈sub〉6〈/sub〉 (M = Co, Ni) alloys are investigated to understand their electronic structure, magnetic character together with thermoelectric behavior using 〈em〉ab-initio〈/em〉 formulism. The variations in physical properties by changing M-site atom are analyzed. The crystal structure of Ba〈sub〉2〈/sub〉MUO〈sub〉6〈/sub〉 (M = Co, Ni) alloys is found to be face-centered cubic (〈em〉Fm-3m〈/em〉) with lattice constant of 0.845 nm for Ba〈sub〉2〈/sub〉CoUO〈sub〉6〈/sub〉 and 0.841 nm for Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉. The band structure and density of states convey half-metallic ferromagnetic character of Ba〈sub〉2〈/sub〉CoUO〈sub〉6〈/sub〉, while Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉 exhibit ferromagnetic semiconducting nature. The electron filling in the 〈em〉d〈/em〉-orbitals of Co and Ni determines the overall electronic and magnetic character of alloys. The obtained structural parameters and magnetic moment are consistent with experimental results. The variation in various thermoelectric parameters with temperature is also examined. The highest value of power factor obtained for Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉 and Ba〈sub〉2〈/sub〉CoUO〈sub〉6〈/sub〉 is 54.92 μW cm〈sup〉−1〈/sup〉 K〈sup〉−2〈/sup〉 and 9.25 μW cm〈sup〉−1〈/sup〉 K〈sup〉−2〈/sup〉, respectively. The semiconducting nature in both spin orientations favors Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉 for thermoelectric applications. The computed elastic constants along with other elastic parameters suggest that these alloys are mechanically stable and possess ductile character.〈/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): Haitao Zhou, Desheng Pan, Yong Li, Da Li, C.J. Choi, Zhidong Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we report the magnetic properties of metal–organic frameworks (MOF) of perovskite-like [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]M(HCOO)〈sub〉3〈/sub〉 (M = Fe〈sup〉II〈/sup〉, Co〈sup〉II〈/sup〉) and niccolite-like [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Fe〈sup〉III〈/sup〉Fe〈sup〉II〈/sup〉(HCOO)〈sub〉6〈/sub〉 synthesized by a solvothermal route. The [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Fe〈sup〉II〈/sup〉(HCOO)〈sub〉3〈/sub〉 exhibits two magnetic transitions at the temperatures of ~19 K for the canted weak ferromagnetic ordering and of ~10 K for the blocking of single-ion quantum magnet due to phase separation, while the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Co〈sup〉II〈/sup〉(HCOO)〈sub〉3〈/sub〉 shows one magnetic transition at the Curie temperature (T〈sub〉C〈/sub〉) of 14.9 K for the canted weak ferromagnetic ordering. Below the T〈sub〉C〈/sub〉 values, spin-flop transition is observed in the magnetization curves of the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]M(HCOO)〈sub〉3〈/sub〉 crystals with the critical magnetic field of about 104 kOe and 90 kOe at 10 K, respectively. Multistep-like jumping magnetization transitions induced by high magnetic field are observed in the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Fe〈sup〉III〈/sup〉Fe〈sup〉II〈/sup〉(HCOO)〈sub〉6〈/sub〉 in a temperature range between 10 and 25 K, indicating a complex spin configuration different from that in the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]M(HCOO)〈sub〉3〈/sub〉 MOFs.〈/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): B. Gokul, P. Saravanan, P. Matheswaran, M. Pandian, R. Sathyamoorthy, K. Asokan, V.T.P. Vinod, Miroslav Černík〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We herein investigate the novel magnetic interactions, such as exchange bias (EB), memory effect (ME) and magnetic relaxation dynamics (MRD) in NiO and 10 wt% Gd doped NiO nanoparticles synthesized by hydrothermal process. X-ray diffraction studies showed crystallization of face-centered-cubic structure for both NiO and Gd-doped NiO nanoparticles. Transmission electron microscopy analysis revealed a spherical morphology for both samples and their mean particle sizes were estimated as 24.5 and 10.3 nm for the pure and Gd-doped NiO nanoparticles, respectively. SQUID magnetic measurements demonstrated the occurrence of large EB coupling: 1.04 and 0.767 kOe; and enhanced coercive fields: 1.75 and 1.27 kOe, for the pure and Gd-doped NiO nanoparticles, respectively. The size-dependent magnetic properties such as, EB, ME and MRD is found to vanish at the average blocking temperature and interestingly, these properties set-in on cooling the samples at 5 K under applied field of 5 kOe. The surface defects such as oxygen vacancies and the Gd〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 impurity phase played a significant role in determining the EB and ME characteristics of NiO nanoparticles.〈/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): S. Sadeghi, S.M. Hamidi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We numerically examine the role of Fano resonance for enhanced magneto-optical effect in an arrayed magneto-plasmonic core-shell structure composed of Bi:YIG cores as a magneto-optical active medium and Au sells as plasmonic ones. The optical and magneto-optical behavior of the magneto-plasmonic core-shell grating structure sustaining Fano resonance is investigated by means of Lumerical software based on the finite-difference time-domain solver. In the proposed structure, Fano resonance arises from the interplay between the guided mode and the surface plasmon resonance which results in enhanced magneto-optical Faraday effect. In addition, the Fano resonance and correspond enhanced magneto-optical effect can be tuned by changing the array period of the structure. The obtained results can be of interest in miniaturized and advanced magneto-optical devices.〈/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): Muhammad Waqas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heat transfer in ferromagnetic stretching flow by moving surface considering a magnetic dipole is elaborated in current research. Rheological relations of non-Newtonian (Williamson) fluid are taken into account for modeling and analysis. Chemical reactions (homogeneous and heterogeneous) are considered for elaboration of mass transportation characteristics. Governing flow expressions are reduced to ODEs by implementing transformation procedure. The well-known bvp4c scheme is used for nonlinear systems computation. Influences of sundry parameters like ferrohydrodynamic interaction parameter, Weissenberg number, homogeneous-heterogeneous reaction parameters, Prandtl number and heat generation parameter on velocity, thermal and solutal fields in addition to coefficient of skin-friction and Nusselt number are displayed via graphs and tabular values. It is revealed that velocity and thermal fields have opposite behavior for ferrohydrodynamic interaction parameter. Besides the heat transportation rate is improved subjected to larger Prandtl number.〈/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): Viktor Ivashko, Oleg Angelsky, Petro Maksimyak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ferromagnetism of nano-graphene layer within Ising model was studied. All results were obtained by using Monte Carlo simulation based on Metropolis algorithm. By applying external magnetic field at room temperature, a gradual transition between ferromagnetic and paramagnetic phases was obtained. This indicates to a potentiality of such a monolayer to be used as a magnetic field sensor. The existence of hysteresis, was established, which strongly depends on the type and magnitude of the interaction strength between the nearest neighbor lattice nodes (spins). Gradual two-step transition between ferromagnetic and paramagnetic phases near absolute zero temperature, was obtained. The results of numerical simulations are in agreement with the available experimental works of other authors.〈/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): L.S. Paixão, G. Rangel, E.O. Usuda, W. Imamura, J.C.G. Tedesco, J.C. Patiño, A.M. Gomes, C.S. Alves, A.M.G. Carvalho〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Since the discovery of the giant magnetocaloric effect in the compound Gd〈sub〉5〈/sub〉Si〈sub〉2〈/sub〉Ge〈sub〉2〈/sub〉, rare earth based intermetallics of the form R〈sub〉5〈/sub〉(Si,Ge)〈sub〉4〈/sub〉 have been largely investigated in their structural and magnetic properties. From the parent compounds Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉 and Nd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉, the present paper reports the magnetic and magnetocaloric properties of the series 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si23.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Gd〈/mi〉〈/mrow〉〈mrow〉〈mn〉5〈/mn〉〈mo〉-〈/mo〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si24.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Nd〈/mi〉〈/mrow〉〈mrow〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉Si〈sub〉4〈/sub〉. Our results indicate that the magnetic moments of the Gd and Nd sublattices are antiparallel, where the moment of each sublattice has almost the same magnitude near 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si25.svg"〉〈mrow〉〈mi〉x〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉4〈/mn〉〈/mrow〉〈/math〉. The antiparallel alignment of the sublattices is detrimental to the magnetocaloric properties of the samples. The end members of the series present larger entropy changes, while for the compound 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si26.svg"〉〈mrow〉〈mi〉x〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉4〈/mn〉〈/mrow〉〈/math〉 such quantity is much lower when compared to all other samples.〈/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): P. Lampen-Kelley, E.M. Clements, B. Casas, M.H. Phan, H. Srikanth, J. Marcin, I. Skorvanek, H.T. Yi, S.W. Cheong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have recently applied the magnetic field and temperature dependence of magnetic entropy change as a probe of the magnetic states of a single crystal of Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 to establish a more comprehensive magnetic phase diagram for this exotic system. The results are consistent with the spin-density wave description of the ground state and indicate the suppression of the modulated state in favor of a ferrimagnetic up-up-down arrangement of the spin chains with the application of a moderate field. We demonstrate, in this study, that the features of the static magnetic phase diagram are preserved when the grain size of Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 is reduced to 440 nm (below the maximum 〈em〉c〈/em〉-axis correlation length of ~550 nm in Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉), although the polycrystalline materials show a non-saturating behavior, rounded steps, and reduced magnetization when compared to the single crystal. Our new finding of the multiple low-temperature magnetization steps in the 440 nm sample, together with conflicting reports concerning such steps in nanostructured samples, suggests that correlations in the 〈em〉ab〈/em〉 plane are more important than correlations along the 〈em〉c〈/em〉-axis in the appearance of the plateaus. The relaxation processes in the system are studied through the decay of remanent magnetization, ac susceptibility, and Argand diagrams. The introduction of grain boundaries in Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 weakens the slow-dynamic state, widens the low-temperature distribution of relaxation times, and lowers activation energies within the Arrhenius-like relaxation regime.〈/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): Baoshan Cui, Hao Wu, Meixia Chang, Jijun Yun, Yalu Zuo, Meizhen Gao, Kang L. Wang, Li Xi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Domain wall (DW) motion via current induced spin-orbit torque (SOT) and/or a magnetic field in ferromagnet/heavy metal heterostructure has attracted abundant interests due to its potential applications in magnetic memories and logic devices. In this work, we study the influence of the depinning energy barrier on DW motion in the creep regime using the polar magneto-optical Kerr microscopy in the Cr layer decorated Pt/Co/Ta structure. We find that although the SOT efficiency shows a significant enhancement in the Pt/Co/Cr/Ta system, but the current-induced DW motion efficiency still shows an attenuation. We confirm that this unexpected result is caused by the enhanced pinning energy barrier, extracted from the relationship between the cumulative depinning probability (〈em〉P〈/em〉〈sub〉d〈/sub〉) and the depinning time (〈em〉t〈/em〉). Moreover, the relationship between 〈em〉P〈/em〉〈sub〉d〈/sub〉 and 〈em〉t〈/em〉 exhibits preferred exponential distribution, indicating that a single energy barrier governs the depinning behavior in our systems. We also reveal that the energy barrier depends on the interface between the ferromagnet and heavy metal. Our study suggests that the current-induced DW motion efficiency is not only determined by the SOT efficiency, but also the depinning energy barrier.〈/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): Ricardo Francisco Alves, Marcio Assolin Correa, Ramon Alves Torquato, Tibério Andrade dos Passos, Felipe Bohn, Rodolfo Bezerra da Silva, Rodinei Medeiros Gomes, Danniel Ferreira de Oliveira〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heusler alloy composed by NiMnIn was prepared by induction melting in Argon atmosphere. The thermal martensitic and magnetic transitions of the sample were identified by differential scanning calorimetry. The quasi-static magnetic properties were observed by field-colled, zero-field-colled, and isothermal magnetization curves in a wide range of temperature. Moreover, AC susceptibility measurements were employed to analyze the low-frequency magnetization dynamics. The martensitic state of the sample leads to magnetic disturbances of quasi-diamagnetism and exchange bias behavior. The exchange bias field presented a transition from negative values to positive values with the temperature increasing. Therefore, the results open a way for technological applications of the NiMnIn Heusler alloy, with potential perspectives for the development of spintronic 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): Krzysztof Tadyszak, Katarzyna Chybczyńska, Paweł Ławniczak, Alina Zalewska, Bogumił Cieniek, Michał Gonet, Marek Murias〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Complex magnetic behavior of pristine, partially reduced graphene oxide aerogel with C/O ratio of 2.35 (EDS) with full analysis of oxygen rich groups attached to the surface is reported. Purity of the system was confirmed by three techniques: elemental analysis, EDS, EPR at 4.2 K none of them detected traces of transition metal ions, especially iron and manganese. Computer tomography reviled the inside foam structure, showing different stacking inside and at the surface, as well as some structural defects. The foams morphology was confirmed by SEM. Electric measurements show linear voltage current relationship and temperature dependences which could be described in the framework of variable range hopping model. Magnetic susceptibility measurements exhibit very weak ferromagnetic behavior modified by antiferromagnetic interactions and paramagnetism. EPR study confirms two component paramagnetism of Curie and Pauli type.〈/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-S0304885318321899-ga1.jpg" width="424" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/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): Yuichi Ishida, Kenji Kondo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigate the skyrmion Hall effect using the Landau-Lifshitz-Gilbert (LLG) equation and the Thiele equation, respectively. Then, we find that these methods give different values for the ratio of in-plane skyrmion velocity components when the Gilbert damping constant is relatively small. Since the Thiele equation is derived from the LLG equation by assuming that the skyrmion structure does not change and behaves like a rigid body, the above result suggests that this assumption does not hold when the Gilbert damping constant is relatively small. Therefore, we conclude that the Thiele equation can not describe the systems precisely under the relatively small Gilbert damping constant due to the distortion of the skyrmion structure and that it is mandatory to solve the LLG equation numerically in order to investigate the skyrmion Hall effect accurately. This result is very important since the Gilbert damping constants of metal materials are generally very small.〈/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): D. Wang, Yan Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spin-orbit torque in magnetic domain walls was studied by solving the Pauli-Schrödinger equation for the itinerant electrons. The Rashba interaction considered is derived from the violation of inversion symmetry at interfaces between ferromagnets and heavy metals. In equilibrium, the Rashba spin-orbit interaction gives rise to a torque corresponding to the Dzyaloshinskii-Moriya interaction. When there is a current flowing, the spin-orbit torque experienced by the itinerant electrons in short domain walls has both field-like and damping-like components. However, when the domain wall width is increased, the damping-like component, which is the counterpart of the non-adiabatic spin transfer torque, decreases rapidly at the domain wall center. In contrast to the non-adiabatic spin transfer torque, the damping-like spin-orbit torque does not approach to zero far away from the domain wall center, even in the adiabatic limit. The scattering of spin-up and spin-down wave functions, which is caused by the Rashba spin-orbit interaction and the spatial variation of magnetization profile in the domain walls, gives rise to the finite damping-like spin-orbit torque.〈/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): Hayato Masumitsu, Soshi Yoshinaga, Yoshifuru Mitsui, Rie Y. Umetsu, Masahiko Hiroi, Yoshiya Uwatoko, Keiichi Koyama〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Substitution effects on weak itinerant electron ferromagnetism in Cr-based ternary alloy CrAlGe were investigated. It was found that substitution of Cr by 3〈em〉d〈/em〉 transition metal with more electrons than Cr enhanced the spontaneous magnetization and Curie temperature. In addition, the itinerancy of CrAlGe was suppressed with the increase of electrons. The ferromagnetism of CrAlGe was related to electron number rather than lattice parameters. The origin of change of itinerancy was suggested to be Coulomb force caused by effective nuclear charge.〈/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): Jun Zhou, Xiangfeng Shu, Yueqin Wang, Jialin Ma, Yin Liu, Ruiwen Shu, Lingbing Kong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉(1−x)CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/xCoFe composites with x = 0.3, 0.4, 0.5, 0.6 were synthesized by using a hydrothermal method. The face-centered cubic structure CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 adheres to the polyhedral CoFe surface due to strong magnetic interaction to form a composite material. The effects of compositions of the CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/CoFe composites on their microwave absorption properties were studied. The sample with a composition of 0.4CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/0.6Co〈sub〉4〈/sub〉Fe〈sub〉6〈/sub〉 showed optimal reflection loss (RL) −58.22 dB at 12.96 GHz, and the matching thickness was 1.45 mm. Meanwhile, it had an effective absorption frequency range of 11.12–15.28 GHz (RL 〈 −10 dB), with a bandwidth of 4.16 GHz, covering the X-band and Ku-band. The enhanced microwave absorption properties of the composites, as compared with the two components, are attributed to the strengthened natural resonance and the increased impedance matching. Most importantly, by adjusting their composition, the CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/CoFe composites can be used as microwave absorbers at C, X or Ku bands. Consequently, these CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/CoFe composites are promising candidates that can be used to design effective microwave absorbers over wide frequency bands.〈/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-S030488531932013X-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/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): M.D. Hossain, M.A. Hossain, M.N.I Khan, S.S. Sikder, M.A. Hakim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Doping of rare earth (RE) ions can influence the magnetic properties in spinel ferrites, whereas the phase formation plays an important role. Therefore, it is important to choose the RE ions for doping content to get more benefit. In this work, synthesis of Yttrium doped Co-Zn ferrites were carried out by the method of solid state reaction. Co〈sub〉0.25〈/sub〉Zn〈sub〉0.75〈/sub〉Y〈sub〉x〈/sub〉Fe〈sub〉2-x〈/sub〉O〈sub〉4〈/sub〉 (CZYF) is the general formula of the studied ferrites where x = 0.00, 0.02, 0.04, 0.06 and 0.08. The structural properties of CZYF ferrites were studied by X-ray diffraction (XRD) technique and further refined by Rietveld method. XRD and Rietveld refinement approved that all the CZYF samples are cubic spinel structure and the lattice parameters were increased with increasing Y content. The variation of grain growth and surface morphology of CZYF samples were studied from SEM images indicated that the average grain size increased from 1.412 µm to 2.341 µm. Frequency dependent magnetic properties (complex permeability, loss factor) were observed in the range of 100 Hz to 120 MHz at 300 K (room temperature). The initial permeability of CZYF ferrites are found to decrease with the increase in Y content. This decrease nature of permeability is related to the increase of porosity and average grain size. At three different temperatures (80 K, 200 K and 300 K), we measured saturation magnetization, coercivity and remanent magnetization. The mentioned properties make CZYF ferrites applicable for use as a soft ferrite.〈/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): S. Divya, K. Jeyadheepan, J. Hemalatha〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetoelectric (ME) nanocomposite flexible films composed of electroactive poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and ferromagnetic cobalt ferrite (CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉) are fabricated. Single-phase nano CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 with cubic spinel structure, synthesized by sol-gel auto combustion technique, is reinforced in different weight percentages to fabricate P(VDF-HFP)-CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 films through spin coating technique. Effect of CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 on structural, morphological, magnetic, ferroelectric, magnetoelectric properties, and giant magnetoresistance (GMR) behavior has been investigated. It is observed that the reinforcement of CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 in P(VDF-HFP) matrix has strongly influenced the formation of β-phase conformation and the degree of structural order. The co-existence of ferroelectric and ferromagnetic orderings in the films has been demonstrated by the P-E and M-H plots. The variations in the polarization effects in the presence of a magnetic field provide the evidence for magnetoelectric cross-coupling in P(VDF-HFP)-CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉. The films exhibit a GMR effect from 7% to 100%. In order to demonstrate the use of ME induced GMR in magnetic field sensing, P(VDF-HFP)-CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 film (10 wt%) is used in a prototype sensor circuit. A good sensing ability and linear response obtained prove that the prepared film can be used as field sensor.〈/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): Ya-nan Zhang, Naisi Zhu, Peng Gao, Yong Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A highly-sensitive magnetic field sensor based on magnetic fluid (MF) infiltrated ring whispering gallery mode (WGM) resonator was proposed and demonstrated in experiment. The resonator was fabricated by attaching a corrosive hollow-core fiber (HCF) to a tapering fiber, which could generate a WGM resonance spectrum. It was firstly demonstrated in theory and experiment that resonance wavelength of the WGM resonator is sensitive to refractive index of medium that infiltrated in the HCF, and the refractive index sensitivity is related to the wall thickness of the HCF. Then, coupling and packaging of the HCF and the tapering fiber were realized by using a simple method, making the sensor robust and portable. When MF was infiltrated in the HCF, since the refractive index of the MF changed with external magnetic field, the WGM resonance valley shifted in wavelength as a function of the magnetic field, which could be used for magnetic field sensing. Experimental results demonstrated that a high sensitivity of 32.4 pm/Gs could be obtained for magnetic field measurement with good linearity. Besides, the proposed sensor behaved simple and robust structure, simple preparation process, low cost, and compact size.〈/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): Mustafa Akyol, Nazan Demiryurek, Onur Iloglu, Kutluhan Utku Tumen, Faruk Karadag, Ahmet Ekicibil〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Y〈sub〉3〈/sub〉Fe〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 shortly named YIG thin film and various form of Au and YIG thin film stacks have been grown on quartz substrate using both spin-coating and sputtering methods. The films are crystallized in cubic phase after heat treatments process that is optimized to avoid cracks on the surface. The thickness of the YIG layer measured by cross-section electron microscope imaging technique are found as about 80 nm for all samples. While the root-mean-square surface roughness of the YIG film is in sub-nanometer scale, it increases up to 2.86 nm by adding Au layer in the film structure. All films exhibit in-plane easy axis and low coercive field at room temperature. But, the saturation magnetization values of films decrease with Au layer. Whereas the optical transmission value is around 80% for YIG samples above 400 nm, it decreases dramatically with Au in the film stacks. The highest absorption coefficient value is found as ~20 × 10〈sup〉4〈/sup〉 cm〈sup〉−1〈/sup〉 in Q/Au/YIG structure. This strong absorption might come from the localized surface plasmon polaritons of Au noble metals in YIG structure because it enhances the electronic transition from crystal field splitting. As a result of these measurements, it is seen that the Au layer reduces the magnetization of the films, while increases the absorption rate significantly. Due to considerably low production cost of YIG in this work, it might open to commonly use of them in the magneto-optical devices.〈/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): Chuangye Yao, Muhammad Ismail, Aize Hao, Santhosh Kumar Thatikonda, Wenhua Huang, Ni Qin, Dinghua Bao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oxygen vacancies derived resistive and magnetic switching, was demonstrated in facile solution-processed Au-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanocomposite thin films, in terms of optimum Au content. The metal element introduced is a unique way to create the optimum amount of oxygen vacancies in the dielectric films even in the absence of electrochemically active electrodes. Compared with pure Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 based device, the RRAM device with Au additives showed bipolar switching behavior with uniform Set/Reset voltages, enhanced endurance of 〉10〈sup〉3〈/sup〉 cycles, and stable time-dependent resistances up to 10〈sup〉4〈/sup〉 s. The introduction of Au nanoparticles caused the oxygen vacancies based confined filament growth for optimum switching uniformity and stability. Results showed that Ohmic conduction was dominant at LRS and Schottky emission was dominated at HRS of the devices. Temperature dependence and magnetization change of various resistance states revealed that resistive and magnetic switching was due to the formation and rupture of conductive filaments of Au atoms confined oxygen vacancies with the conversion of cation valence states (Co〈sup〉2+〈/sup〉 and Co〈sup〉3+〈/sup〉). The present study suggests that Au-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanocomposite thin films have a potential for future multifunctional electromagnetic integrated device applications.〈/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): Kai Sun, Shuai Feng, Qian Jiang, Xiaofeng Li, Yaping Li, Runhua Fan, Yan An, Jiaqi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The soft magnetic composites (SMCs) with high saturation magnetic flux density (〈em〉B〈/em〉〈sub〉s〈/sub〉) and low core loss (〈em〉P〈/em〉〈sub〉s〈/sub〉) have great potential in power electronics. In this work, the insulating SiO〈sub〉2〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 layer was prepared by a hydro-thermal method to coat on the surface of the carbonyl iron powders (CIPs). Then, the coated CIPs were heterogeneously distributed in the reduced iron powders (RIPs) to fabricate the intergranular insulated SMCs. The scanning electron microscope (SEM) images and elements analysis confirmed that the surface of the CIPs was covered by a thin insulating layer forming a core-shell structure, and the Si-O-Al bond was detected by FTIR spectra. The resulting samples were annealed at 450 °C in N〈sub〉2〈/sub〉 atmosphere to eliminate the residual stress and improve magnetic properties. The annealed.〈/p〉 〈p〉SMCs containing 25 wt% CIPs@SiO〈sub〉2〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 have optimum magnetic properties with a low 〈em〉P〈/em〉〈sub〉s〈/sub〉 of 106.9 W/kg and a highly approximate 〈em〉B〈/em〉〈sub〉s〈/sub〉 of 1.28 T (measured at 500 Hz). Compared with the conventional SMCs, the addition of the coated CIPs can suppress the adverse effect of the nonmagnetic coating layer on magnetic properties; meanwhile, the coated CIPs distributed in the RIPs can reduce the 〈em〉P〈/em〉〈sub〉s〈/sub〉. This work provides a promising approach to the development of SMCs with low hysteresis loss and optimum magnetic properties at low frequency.〈/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): Shyamaldas, M. Bououdina, C. Manoharan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pure cobalt ferrite nanoparticles were synthesised by hydrothermal method. Cubic spinel structure and improved crystallinity was confirmed by X-ray diffraction analysis. Morphology and average particle size within thenanorange were identified by SEM and TEM. EDX confirmed the presence of Fe, Co, and O elements without any impurities. FT-IR analysis confirmed the presence of vibrational bands in the range of 581–590 cm〈sup〉−1〈/sup〉 and 424–468 cm〈sup〉−1〈/sup〉 ascribed to Fe〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O and Co〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O bonds, respectively. The presence of five Raman active modes confirmed the cubic spinel-type structure. Optical study revealed the influence of higher annealing temperature on the band gap; it decreases from 2.60 to 1.53 eV. The dielectric constant, dielectric loss and ac-conductivity were found to varywith increasing frequency range. The shifting of cations between tetrahedral (A) to octahedral (B) sites and vice versa was revealed by Mossbauer spectroscopy. The observed sextets proposed that CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 nanoparticles are highly crystalline and magnetically ordered. With increasing annealing temperature, both saturation magnetization and remanence increased, while the coercivity was reduced, which is due to the transition from single domain to multidomain on crossing the critical size of ~40 nm. The Cyclic Voltammetry (CV) test of nanoparticles annealed at 800 °C (S3) revealed excellent specific capacitance at low scan rate.〈/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-S0304885319317615-ga1.jpg" width="299" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/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): Xiangxia Wei, Yinhua Liu, Dongjie Zhao, Xuewei Mao, Wanyue Jiang, Shuzhi Sam Ge〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Net-shaped hexagonal barium and strontium ferrites with desirable shapes have been successfully fabricated by the extrusion-based three-dimensional (3D) printing. The influence of milling and calcination conditions on magnetic properties of as-printed hexaferrites are systematically investigated by vibrating sample magnetometry (VSM). The typical ferromagnetic hysteresis loops are observed, revealing that the resulting bulk ferrites derived from the preliminary milled powders are prefect hard magnetic materials. In particular, it is clear that the saturation magnetization is very close to the theoretical values after calcinations. Moreover, the coercivity can be effectively enhanced in the range of 4–6 kOe upon thermal treatment, which is a much higher value compared to ferrites prepared by the conventional ceramic processing. More importantly, the maximum energy product can be significantly improved to as high as around 2.5 MGOe for the 3D-printed strontium ferrites. This is attributed not only to fine precursor powders subjected to mechanical milling, but also to the optimized annealing for grain growth with sizes near the critical single domain limit. Overall, the fabrication of bulk ferrites derived from milled powders using the 3D printing is attractive for the large-scale applications, and may also pave the way for some specific applications, for instance, magnetic separation for nanoparticles.〈/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): Aquil Ahmad, S.K. Srivastava, A.K. Das〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The generalized gradient approximation (GGA) scheme in the first-principles calculations is used to study the effect of L2〈sub〉1〈/sub〉 and XA ordering on the phase stability, half-metallicity and magnetism of Co〈sub〉2〈/sub〉FeAl (CFA) Heusler alloy. Various possible hypothetical structures: L2〈sub〉1〈/sub〉-I, L2〈sub〉1〈/sub〉-II, XA-I, and XA-II are prepared under the conventional L2〈sub〉1〈/sub〉 and inverse XA phases by altering the atomic occupancies at their Wyckoff sites. It is found that the XA-II phase of CFA is the most stable phase energetically among all the structures. The electronic structure calculations without U show the presence of half-metallic (HM) ground state only in L2〈sub〉1〈/sub〉-I structure and the other structures are found to be metallic. However, the electronic structures of CFA are significantly modified in the presence of U, although the total magnetic moments per cell remained the same and consistent with the Slater-Pauling (SP) rule. The metallic ground states of CFA in L2〈sub〉1〈/sub〉-II and XA-II structures are converted into the half-metallic ground states in presence of U but remained the same (metallic) in XA-I structure. The results indicate that the electronic structures are not only dependent on the L2〈sub〉1〈/sub〉 and XA ordering of the atoms but also depend on the choice of U values. So experiments may only verify the superiority of GGA + U to GGA.〈/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): I.V. Kozlov, G.N. Elmanov, K.E. Prikhodko, L.V. Kutuzov, B.A. Tarasov, V.V. Mikhalchik, R.D. Svetogorov, V.S. Mashera, E.S. Gorelikov, S.A. Gudoshnikov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Amorphous Co〈sub〉69〈/sub〉Fe〈sub〉4〈/sub〉Cr〈sub〉4〈/sub〉Si〈sub〉12〈/sub〉B〈sub〉11〈/sub〉 glass-coated microwires after heat treatment in the temperature range of 250–600 °C during 30 min were investigated. Changes of microstructure, phase composition, fracture morphology, and giant magnetoimpedance (GMI) properties were shown. It is confirmed that a significant increase in the GMI effect was possible not only due to the structural relaxation, but also as a result of phase transformations at the temperature close to the onset of crystallization. It is shown that at the very initial stage of the nucleation of Co nanocrystals, a sharp increase in circumferential diagonal GMI component was observed, a further increase in the amount of the crystalline Co phase was accompanied by degradation of this effect. The most significant GMI ratio was obtained for microwires annealed at 430 °C. At 450 °C and above, an irreversible decrease of the GMI ratio took place. It was caused by the formation of Co crystals, decrease in amount and composition change of the amorphous phase during primary and secondary crystallization. At the final stage of the Co crystals segregation the secondary crystallization of the residual amorphous phase occurred with formation of a metastable τ-phase with a Me〈sub〉23〈/sub〉B〈sub〉6〈/sub〉 type structure. Thermal stability of the τ-phase was analyzed.〈/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): S. Pütter〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The thickness-driven spin-reorientation transition of Co/Au(1 1 1) is studied via 〈em〉in situ〈/em〉 Kerr microscopy. On varying the premagnetization conditions in external field of in-plane or normal orientation, the magnetic switching into a final remanent state from an in-plane field is investigated. The quantitative analysis of the Kerr rotation derived from Kerr microscopy images allows the determination of the population of different magnetic phases as a function of thickness. Coexisting magnetic phases with preferred in-plane and out-of-plane magnetization orientation are identified. The overall switching behaviour is explained by thermal activation of magnetic domains. We show that there is a population of orthogonal bistable magnetic domains, which can be remanently switched between out-of-plane and in-plane orientation by the appropriate magnetic field. This quantity is related to the intersection of the population of states for in-plane and out-of-plane magnetization.〈/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. Peña-Garcia, Y. Guerra, F.E.P. Santos, L.C. Almeida, E. Padrón-Hernández〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a study about the structural and magnetic properties of Ni-doped yttrium iron garnet nanopowders synthesized by sol-gel. The Rietveld refinement of the X-ray diffractograms indicates the replacement of Fe by Ni in the tetrahedral (〈em〉d〈/em〉) and octahedral (〈em〉a〈/em〉) sites of yttrium iron garnet (YIG) structure. The lattice parameter showed variation associated to the effects of Ni inclusion and structural defects, such as, oxygen vacancies. The morphological analysis evidence particles with a cylindrical shape and the Energy Dispersive Spectroscopy results corroborate the presence of Ni. The average porosity suggests that the replacement of Fe by Ni does not substantially change the textural properties of the particles. The Fourier transform infrared and Raman spectroscopies showed the characteristic absorption bands of YIG and confirmed the substitution in the 〈em〉a〈/em〉-sites and 〈em〉d〈/em〉-sites. The saturation magnetization was studied from the hysteresis loops measurements and present variations with the dopant concentration, associated to the replacement of Fe by Ni and to the oxygen vacancies occurrence. Changes in the coercive field for different dopant concentration were associated to the particle size and pinning centers existence.〈/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-S0304885318328610-ga1.jpg" width="379" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Michał Kozanecki, Czesław Rudowicz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recent developments in high-magnetic field/high-frequency electron magnetic resonance (HMF-EMR) techniques offer improved capabilities for determination of the spin Hamiltonian (SH) parameters, including the fourth-rank zero field splitting (ZFS) parameters (ZFSPs) for spin 〈em〉S̃〈/em〉 = 2 systems. However, the density functional theory (DFT) and ab-initio methods provide predictions of the ZFS energies from which usually only the second-rank ZFSPs are obtained. Here we present an analytical method for determination of the fourth-rank ZFSPs from the ZFS energy levels for 〈em〉S̃〈/em〉 = 2 ions at orthorhombic sites. This enables assessment of their significance and determination of the dominant parameters. Applications of this method for Fe〈sup〉2+〈/sup〉 in [Fe(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉](NH〈sub〉4〈/sub〉)〈sub〉2〈/sub〉(SO4)〈sub〉2〈/sub〉, Fe〈sup〉2+〈/sup〉 in forsterite (Fe〈sup〉2+〈/sup〉:Mg〈sub〉2〈/sub〉SiO〈sub〉4〈/sub〉), and Cr〈sup〉2+〈/sup〉 ions in (ND〈sub〉4〈/sub〉)〈sub〉2〈/sub〉Cr(D〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉 and Rb〈sub〉2〈/sub〉Cr(D〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉 indicate important role the fourth-rank ZFSPs. The analytical formulas derived by us may be applied to other 3d〈sup〉6〈/sup〉 and 3d〈sup〉4〈/sup〉 (〈em〉S̃〈/em〉 = 2) ions at orthorhombic sites in various hosts for better modeling of spectroscopic and magnetic properties of these systems.〈/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): Kingshuk Mallick, Aditya A. Wagh, P.S. Anil Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We observe an exchange bias at low temperatures in polycrystalline ferrimagnetic MgFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 (MFO) films grown on Si(100), emerging from Antiferromagnetic (AFM)-like interactions at defect sites, concentrated predominantly at the grain boundaries. In this report, we show it is possible to utilize these AFM interactions to get enhanced spin transport utilizing the spin Seebeck effect (SSE). The temperature dependence of the SSE signal in two films with different defect densities allowed us to identify a unique temperature window for both films where an enhanced SSE signal was observed. Such enhancement has been reported in different Ferromagnet (FM)/AFM bilayer systems, but its observation in a single layer hosting both FM-AFM interactions makes our results attractive. Temperature dependent SQUID magnetometry revealed two distinct regions of strong and weak coupling for the FM-AFM interactions. The weak coupling region is characterized by a distribution of AFM energy barriers (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈/mrow〉〈/math〉E), which can modify the spin conductance across the FM-AFM boundary and hence, affect the spin transport. Indeed, we find that the same functional form fits both the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈/mrow〉〈/math〉E distribution and the SSE temperature evolution for both films. This study should aid in the understanding of SSE in the large class of polycrystalline materials with inherent growth induced defect densities and illustrate the significance of magnetically disordered phases in spin transport.〈/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): Takahide Kubota, Zhenchao Wen, Koki Takanashi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A half-metal is an ideal spin source to realize extremely large magnetoresistance effects because of the completely spin-polarized density of states at the Fermi level, and Heusler alloy is a material class for which several compositions are known to exhibit half-metallic properties. Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effect is a resistance change that depends upon the relative angle of the magnetization vectors in magnetic layers separated by thin non-magnetic layer(s), which can be utilized for magnetic sensor applications. Over the last decade, the resistance change of CPP-GMR has been found to enhance greatly when using half-metallic Heusler alloys. In this article, the history of Heusler alloy based CPP-GMR is briefly reviewed, including the authors’ recent results on the analysis of the spin asymmetry coefficients based on the Valet-Fert model. Finally, the degradation of half-metallic spin polarization at interfaces is discussed and a future prospect is described.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): M. Ozcan, S. Ozen, M. Yagmurcukardes, H. Sahin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Novel stable ultra-thin phases of europium oxide are investigated by means of state-of-the-art first principles calculations. Total energy calculations show that single layers of EuO〈sub〉2〈/sub〉 and Eu(OH)〈sub〉2〈/sub〉 can be stabilized in an octahedrally coordinated (1T) atomic structure. However, phonon calculations reveal that although both structures are energetically feasible, only the 1T-EuO〈sub〉2〈/sub〉 phase has dynamical stability. The phonon spectrum of 1T-EuO〈sub〉2〈/sub〉 displays three Raman active modes; a non-degenerate out-of-plane 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉A〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈mi〉g〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 mode at 353.5 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉cm〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 and two doubly-degenerate in-plane 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉E〈/mi〉〈/mrow〉〈mrow〉〈mi〉g〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 modes at 304.3 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉cm〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉. Furthermore, magnetic ground state and electronic band dispersion calculations show that the single layer EuO〈sub〉2〈/sub〉 is a metal with net magnetic moment of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈msub〉〈mrow〉〈mn〉5〈/mn〉〈/mrow〉〈mrow〉〈mi〉μ〈/mi〉〈mi〉B〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 per unitcell resulting in a half-metallic ferrimagnetic behavior. Moreover, robustness of the half-metallic ferrimagnetic characteristics of EuO〈sub〉2〈/sub〉 is confirmed by the application of electric field and charging. Single layer 1T-EuO〈sub〉2〈/sub〉, with its stable ultra-thin structure and half-metallic ferrimagnetic feature, is a promising novel material for nanoscale electronic and 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): Jianlei Shen, Qingqi Zeng, Hongguo Zhang, Xuekui Xi, Enke Liu, Wenhong Wang, Guangheng Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, new all-〈em〉d〈/em〉-metal Heusler alloys Fe〈sub〉50−x〈/sub〉Cr〈sub〉25+x〈/sub〉V〈sub〉25〈/sub〉 (x = 0–25) were investigated on the behaviors of atomic configuration, lattice constant change, and ferromagnetism from the aspects of theoretical calculations and experiments. The theoretical calculations found that both end-member compounds Fe〈sub〉50〈/sub〉Cr〈sub〉25〈/sub〉V〈sub〉25〈/sub〉 (x = 0) and Cr〈sub〉50〈/sub〉Fe〈sub〉25〈/sub〉V〈sub〉25〈/sub〉 (x = 25) prefer to crystallize in Hg〈sub〉2〈/sub〉CuTi-type (space group: 216) structure rather than Cu〈sub〉2〈/sub〉MnAl-type (space group: 225) one. During the whole substitution process, the structure of Fe〈sub〉50−x〈/sub〉Cr〈sub〉25+x〈/sub〉V〈sub〉25〈/sub〉 alloys remains Hg〈sub〉2〈/sub〉CuTi-type structure, taking the path from 216 to 216, but with different degrees of BC-site disorder. Both the experimental and theoretical results reveal that the lattice constant increases first, and then abnormally decreases, showing a maximum at Cr40, due to the enhanced covalent 〈em〉d〈/em〉-〈em〉d〈/em〉 hybridizations between the transition metals. The magnetic moment and Curie temperature tuned by Cr substitution vary remarkably between 3.3 and 1.15 μ〈sub〉B〈/sub〉/f.u. and between 700 and 170 K, respectively, which indicates that the Cr substitution for Fe alters the spin polarizations and exchange interactions in the system. These results provide new insights into the atomic configuration, magnetism and bonding effect in all-〈em〉d〈/em〉-metal Heusler alloys based on the 〈em〉d〈/em〉-〈em〉d〈/em〉 hybridizations.〈/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. Sarathbavan, Hanuma Kumar Dara, Tripta Parida, K. Ramamurthi, K. Kamala Bharathi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report on temperature dependent magnetization and anisotropy properties, magnetic interactions at low temperatures, high temperature magnetic properties and frequency dependent dielectric properties of 0.3NiFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉–0.7Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 nanocomposites. X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) techniques are employed to study the crystal structure, morphology and the chemical state of the NiFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 (NFO) nanoparticles, Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 (NBTO) nanorods and nanocomposites. XRD and Raman spectroscopy studies indicate the formation of NFO, NBTO and the nanocomposites in pure phase. SEM and TEM images indicates the presence of both nanoparticles (from NFO) and nanorods (from NBTO) in the 0.3NiFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉–0.7Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 nanocomposites and the lattice planes with respect to both the phases are confirmed from the selected area diffraction pattern. Magnetization measurements at various temperatures (300 K, 40 K, 10 K and 2 K), field cooled (FC) and zero field cooled (ZFC) magnetization from 300 K to 2 K are measured for the nanocomposites. Saturation magnetization value at 300 K and 2 K for the nanocomposites is seen to be 14.62 emu/g and 16.80 emu/g respectively. Existence of spin glass behavior and competing magnetic interactions in the 0.3NiFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉–0.7Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 nanocomposites is confirmed from the ZFC and FC magnetization studies. Curie temperature value for 0.3NiFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉–0.7Na〈sub〉0.5〈/sub〉Bi〈sub〉0.5〈/sub〉TiO〈sub〉3〈/sub〉 nanocomposites is observed to be 900 K. Frequency dependent dielectric studies shows the relaxation behavior of the nanocomposites with two relaxation times of 5.803 × 10〈sup〉−2〈/sup〉 s and 2.770 × 10〈sup〉−4〈/sup〉 s arising from NFO and NBTO phases.〈/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-S0304885319321961-ga1.jpg" width="499" 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): Archana Kumari, C. Dhanasekhar, A.K. Das〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The structural, magnetic and transport properties of the layered RBaCo〈sub〉2〈/sub〉O〈sub〉5.5±δ〈/sub〉 cobaltites are sensitive to the oxygen stoichiometry. In this present study, we report the presence of a low-temperature magnetic glassy state in electron-doped polycrystalline YBaCo〈sub〉2〈/sub〉O〈sub〉5.5〈/sub〉 cobaltite. The ac magnetization studies show the absence of conventional spin glass features, while the various dc magnetization studies demonstrate the presence of non-equilibrium magnetic glassy state at low temperature. The magnetic glassy state of this sample results from the kinetic arrest of the first order ferro (or ferri) to antiferromagnetic transition. The role of electron doping in the occurrence of magnetic glassy phenomena is discussed in terms of magnetic phase separation involving the Co〈sup〉3+〈/sup〉/Co〈sup〉2+〈/sup〉 clusters of the ferrimagnetic phase in the Co〈sup〉3+〈/sup〉/Co〈sup〉3+〈/sup〉 antiferromagnetic matrix.〈/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): Xu Zheng, Tian Gao, Wei Jing, Xingyu Wang, Yongsheng Liu, Bin Chen, Hongliang Dong, Zhiqiang Chen, Shixun Cao, Chuanbing Cai, Vyacheslav V. Marchenkov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic properties of polycrystalline La〈sub〉1-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Ca〈em〉〈sub〉x〈/sub〉〈/em〉Mn〈sub〉0.9〈/sub〉Cu〈sub〉0.1〈/sub〉O〈sub〉3〈/sub〉 (0.02 ≤ 〈em〉x〈/em〉 ≤ 0.4) have been investigated in detail. All samples show a clear ferromagnetic-paramagnetic transition. The Curie temperature 〈em〉T〈/em〉〈sub〉C〈/sub〉 decreases with increasing Ca-dopant. Inverse susceptibility of all the samples deviates from Curie-Weiss law above 〈em〉T〈/em〉〈sub〉C〈/sub〉, indicating the presence of a short range ferromagnetic and/or antiferromagnetic ordering state in the paramagnetic background. For 0.02 ≤ 〈em〉x〈/em〉 ≤ 0.2, the upward deviation is attributed to antiferromagnetic interactions, while the downward for 〈em〉x〈/em〉 ≥ 0.3 samples is caused by a Griffiths-like behavior, which is suppressed by an applied field. A charge ordering transition associated with an antiferromagnetic phase is detected in 〈em〉x〈/em〉 ≥ 0.3 samples, the melting of which results in a spin reorientation transition and a new FM phase. Finally, the phase diagrams of this manganite system have been established.〈/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): Jae-Hyoung You, Sungjoon Choi, Seung-young Park, Sang-Im Yoo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A partial substitution of Zn〈sup〉2+〈/sup〉 for the Fe〈sup〉2+〈/sup〉 site of BaY-type hexaferrite was found to be effective for the improvement of microwave absorption properties in 0.5–18 GHz. For this study, the composites of polycrystalline Ba〈sub〉2〈/sub〉Fe〈sub〉2-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Zn〈em〉〈sub〉x〈/sub〉〈/em〉Fe〈sub〉12〈/sub〉O〈sub〉22〈/sub〉 (Ba〈sub〉2〈/sub〉Fe〈sub〉2-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Zn〈em〉〈sub〉x〈/sub〉〈/em〉Y, 0.5 ≤ 〈em〉x〈/em〉 ≤ 2.0) and epoxy resin were fabricated with various hexaferrite volume fractions (〈em〉V〈/em〉〈sub〉f〈/sub〉) of 30–90%. As a result, Ba〈sub〉2〈/sub〉Zn〈em〉〈sub〉x〈/sub〉〈/em〉Fe〈sub〉2-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Y (〈em〉x〈/em〉 = 0.5–1.5) composites having the partial substitution of Zn〈sup〉2+〈/sup〉 exhibited larger complex permittivity values than fully Zn〈sup〉2+〈/sup〉 substituted composite of Ba〈sub〉2〈/sub〉Zn〈sub〉2〈/sub〉Y (〈em〉x〈/em〉 = 2.0) due to an electron hopping between Fe〈sup〉2+〈/sup〉 and Fe〈sup〉3+〈/sup〉 ions. Because of the enhanced permittivity, Ba〈sub〉2〈/sub〉Fe〈sub〉2-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Zn〈em〉〈sub〉x〈/sub〉〈/em〉Y (〈em〉x〈/em〉 = 0.5–1.5) composites with 30% of 〈em〉V〈/em〉〈sub〉f〈/sub〉 possessed better impedance matching characteristics compared with other composites having larger 〈em〉V〈/em〉〈sub〉f〈/sub〉 values. Consequently, Ba〈sub〉2〈/sub〉Fe〈sub〉2-〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉Zn〈em〉〈sub〉x〈/sub〉〈/em〉Y (〈em〉x〈/em〉 = 0.5–1.5) composites exhibited excellent RL values lower than −50 dB with the thickness values ranging from 1.52 to 1.80 mm.〈/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): Jia-hao Liu, Xiao-kuo Yang, Huan-qing Cui, Bo Wei, Cheng Li, Yabo Chen, Mingliang Zhang, Chuang Li, Dan-na Dong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fast 180° magnetization switching is one of the main challenges for straintronics to be used in magnetic storage and logic. By deflecting the electrodes pair axis by a small angle from the long axis of a uniaxial multiferroic nanomagnet, the voltage pulse can directly induce the nanomagnet to complete repeatable 180° switchings without requiring a start-up time. The dynamic magnetization of the repeatable 180° switching in the nanomagnet and the optimal voltage pulse waveform is simulated through micromagnetic method. Is obtained by simulation calculation, when the electrodes pair axis tilting angle is about 5°, the required stress is small, the switching frequency is high, and the initial switching time is short, which is about 1/5 of the existing research scheme. The switching at room temperature is also calculated by a mathematical model. The switching time is longer under the influence of thermal fluctuations. These findings may provide guidance for the application of straintronic devices.〈/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): Maria M. Markina, Konstantin V. Zakharov, Peter S. Berdonosov, Valery A. Dolgikh, Elena S. Kuznetsova, Sergei A. Klimin, Oleg B. Yumashev, Alexander N. Vasiliev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The kagome lattice of copper ions in francisite-type compounds is quite sensitive to external stimuli, being easily affected by temperature and magnetic field. The rare-earth ions inserted between buckled layers of transition metal add new dimension to magnetism in these systems. Neodymium francisites, Cu〈sub〉3〈/sub〉Nd(SeO〈sub〉3〈/sub〉)〈sub〉2〈/sub〉O〈sub〉2〈/sub〉X (X = Cl, Br), experience long range magnetic order at 〈em〉T〈/em〉〈sub〉N〈/sub〉 = 34 K (Cl) or 35.2 K (Br) and spin reorientation transition at 〈em〉T〈/em〉〈sub〉R〈/sub〉 = 4 K (Cl) or 4.6 K (Br) marked by sharp anomalies in magnetization 〈em〉M〈/em〉, specific heat 〈em〉C〈/em〉〈sub〉p〈/sub〉, and optical spectra. The spin reorientation of Cu〈sup〉2+〈/sup〉 ions is due to 〈em〉d〈/em〉-〈em〉f〈/em〉 interaction of transition and rare-earth magnetic subsystems. Under action of modest external field 〈em〉B〈/em〉 〈 2 T both compounds exhibit metamagnetic phase transition, largely hysteretic in case of Cl compound at 〈em〉T〈/em〉 〈 〈em〉T〈/em〉〈sub〉R〈/sub〉.〈/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-S0304885319321328-ga1.jpg" width="285" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/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): Seyedeh Mansoureh Hashemi, Saeed Hasani, Khadijeh Jahanbani Ardakani, Fatemeh Davar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, cobalt ferrite (CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉) nanoparticles were synthesized by a novel sol-gel auto-combustion in the simultaneous presence of ethylene glycol and agarose as complexing agents, and their effects on the structure, morphology, and magnetic properties of this ferrite were investigated. All synthesized nanoparticles were structurally and morphologically characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Fourier transform infrared spectroscopy (FT-IR) methods. The results confirmed that the single-phase spinel CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 nanoparticles were obtained. Analysis of the XRD patterns was carried out by Rietveld refinement technique to estimate the particle size, lattice parameter, and the cation distribution between the tetrahedral and octahedral sites. The Rietveld refinement data revealed that the simultaneous presence of ethylene glycol and agarose reduced the average size of crystallites. Moreover, FE-SEM micrographs showed that the agglomeration of the nanoparticles was reduced by the addition of these agents. Magnetic characteristics of the synthesized nanoparticles were characterized by a vibrating sample magnetometer (VSM). The results revealed that the saturation magnetization and coercivity could simultaneously be increased by the proper addition of ethylene glycol and agarose, so that these magnetic properties can be used to design magnetic coding and sensing devices.〈/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): Peng Zhao, Gang Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on density functional theory combined with Keldysh non-equilibrium Green’s function formalism, we investigate the spin-polarized transport properties of planar four-coordinate Fe complexes-based molecular devices with carbon nanotube bridges and electrodes. The results show that these systems can exhibit perfect spin filtering, large giant magnetoresistance and low-bias negative differential resistance effects with the external magnetic field modulation. The underlying mechanism is analyzed by spin-resolved transmission spectra, projected density of states, and spatial distributions of corresponding molecular projected self-consistent Hamiltonian orbitals. On the basis of these intriguing transport properties, we further design basic spin molecular Boolean logic gates, such as YES, NOT, AND, NAND, XOR, NXOR, OR and NOR logic gates.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Based on the intriguing spin-polarized transport properties of PFCF-based molecular devices with carbon nanotube bridges and electrodes, basic spin molecular Boolean logic gates are designed.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885319324552-ga1.jpg" width="459" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): M.M. van de Loosdrecht, S. Waanders, H.J.G. Krooshoop, B. ten Haken〈/p〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Jun He, Dongyong Shan, Shuoqing Yan, Heng Luo, Can Cao, Yuhui Peng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene is highly desirable as a potential microwave absorbent due to its positive dielectric loss ability. However, lack of magnetic loss for pure Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene results in unbalanced electromagnetic parameters and poor impedance matching. In this paper, the laminated Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene was synthesized using HF etching process. Then, the magnetic FeCo-decorated Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene (FeCo-Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene) composite was fabricated for the first time via a in-situ hydrothermal method. The incorporation of magnetic FeCo nanoparticles on Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene can enhance microwave absorption property. Specifically, the FeCo-Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene composite displayed a broad effective bandwidth (RL 〈 −10 dB) of 8.8 GHz with only 1.6 mm. This excellent microwave absorbing performance was mainly attributed to strong microwave attenuation ability and improved impedance matching. The results of this work confirm that the FeCo-Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉 MXene composite could be favourable as highly competitive microwave absorbent.〈/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): Roland H. Tarkhanyan, Dimitris G. Niarchos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The influence of the magnetic field on the thermoelectric figure of merit in semiconducting materials is studied theoretically. One of the important issues is the urgency to distinguish the various conditions under which the magneto-thermoelectric effects can be observed. Isothermal effects take place when there is no temperature gradient in the direction perpendicular to the plane containing the magnetic field and applied temperature gradient. Adiabatic effects occur when there is no heat current in the same transverse direction while a temperature gradient arises due to the Righi-Leduc effect. In this paper we examine how the application of an external magnetic field can vary the figure of merit 〈em〉ZT〈/em〉 under isothermal and adiabatic conditions and establish relations among them for both longitudinal and transverse Nernst-Ettingshausen effects. Analytical expressions for the figures of merit are obtained in semiconductors with both non-degenerate and strongly degenerate statistics of charge carriers, in limiting cases of weak and classically strong magnetic fields.〈/p〉〈/div〉 〈/div〉