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Rare Metals 2021年第5期40卷 1232-1238页

作者： Tian-Chi Ji Min-Xiang Pan Hong-Liang Ge Qiong Wu Peng-Yue Zhang Magnetism Key Laboratory of Zhejiang Province China Jiliang UniversityHangzhou 310018China

In the present work,the magnetization reversal behavior for the melt spinning(Nd_(0.8)Ce_(0.2))_(2)Fe_(12)Co_(2-x)Zr_(x)B(x=0,0.5)permanent alloys with high coercivity was investigated by analyzing the hysteresis curves and the recoil *** to the Zr-free alloy,the Zr-doped sample obtains higher magnetic properties:coercivity of H_(cj)=650.5 kA·m^(-1),squareness of H_(k)/H_(cj)=0.76 and maximum energy product of(BH)_(max)=131.0 kJ·m^(-3).The first-order reversal curves(FORCs)analysis was taken to identify optimal conditions of exchange coupling for the Zr-free and Zr-doped *** coercivity mechanism of theα-Fe/Nd_(2)Fe_(14)B nanocomposite alloys was analyzed by the angular dependence of the coercive field as measured for the Zr-doped *** results show that the magnetic reverse process of the Zr-doped sample can be explained by the pinning model.

关键词： magnetization reversal Coercivity mechanism First-order reversal curve(FORC) Nanocomposite

Magnetoresistive behavior and magnetization reversal of NiFe/Cu/CoFe/IrMn spin valve GMRs in nanoscale

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International Journal of Minerals,Metallurgy and Materials 2013年第7期20卷 700-704页

作者： Cong Yin Ze Jia Wei-chao Ma Tian-ling Ren Institute of Microelectronics & Tsinghua National Laboratory for Information Science and Technology Tsinghua University

The magnetoresistance behavior and the magnetization reversal mode of NiFe/Cu/CoFe/IrMn spin valve giant magnetoresistance （SV-GMR） in nanoscale were investigated experimentally and theoretically by nanosized magnetic simulation methods. Based on the Landau-Lifshitz-Gilbert equation, a model with a special gridding was proposed to calculate the giant magnetoresistance ratio （MR） and investigate the magnetization reversal mode. The relationship between MR and the external magnetic field was obtained and analyzed. Studies into the variation of the magnetization distribution reveal that the magnetization reversal mode, that is, the jump variation mode for NiFe/Cu/CoFe/IrMn, depends greatly on the antiferromagnetic coupling behavior between the pinned layer and the antiferromagnetic layer. It is also found that the switching field is almost linear with the exchange coefficient.

关键词： giant magnetoresistance (GMR) spin valves nanoscale magnetization reversal

Magnetic anisotropy and magnetization reversal of ultrathin iron films with in-plane magnetization on Si（111） substrates

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Chinese Physics B 2012年第7期21卷 5-10页

作者：刘郝亮何为杜海峰房亚鹏吴琼张向群杨海涛成昭华 State Key Laboratory of Magnetism and Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China

The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer （ML） grown on Si（111） have been investigated by ferromagnetic resonance （FMR） and vibrating sample magnetometer （VSM）. Owing to the significant modification of the energy surface in remanent state by slight misorientation from （111） plane and a uniaxial magnetic anisotropy, the azimuthal angular dependence of in-plane resonance field shows a six-fold symmetry with a weak uniaxial contribution, while the remanence of hysteresis loops displays a two-fold one. The competition between the first and second magnetoerystalline anisotropies may result in the switching of in-plane easy axis of the system. Combining the FMR and VSM measurements, the magnetization reversal mechanism has also been determined.

关键词： magnetic anisotropy magnetization reversal ultrathin film

Thermally activated magnetization reversal in magnetic tunnel junctions

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Chinese Physics B 2009年第2期18卷 790-794页

作者：周广宏王寅岗祁先进李子全陈建康 School of Materials Science and TechnoloJingy Nanjing University of Aeronautics and Astronautics Department of Mechanical Engineering Huaiyin Institute of Technology

In this paper, the magnetization reversal of the ferromagnetic layers in the IrMn/CoFe/AlOx/CoFe magnetic tunnel junction has been investigated using bulk magnetometry. The films exhibit very complex magnetization processes and reversal mechanism. Thermal activation phenomena such as the training effect, the asymmetry of reversal, the loop broadening and the decrease of exchange field while holding the film at negative saturation have been observed on the hysteresis loops of the pinned ferromagnetic layer while not on those of the free ferromagnetic layer. The thermal activation phenomena observed can be explained by the model of two energy barrier distributions with different time constants.

关键词： magnetic tunnel junctions magnetization reversal thermal activation exchange cou~ pling

In-plane current-induced magnetization reversal of Pd/CoZr/MgO magnetic multilayers

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Chinese Physics B 2022年第12期31卷 511-515页

作者： Jing Liu Caiyin You Li Ma Yun Li Ling Ma Na Tian School of Materials Science and Engineering Xi’an University of TechnologyXi’an 710048China

High critical current density(>10^(6)A/cm^(2))is one of major obstacles to realize practical applications of the currentdriven magnetization reversal *** this work,we successfully prepared Pd/CoZr(3.5 nm)/MgO thin films with large perpendicular magnetic anisotropy and demonstrated a way of reducing the critical current density with a low out-of-plane magnetic field in the Pd/CoZr/MgO *** the assistance of an out-of-plane magnetic field,the magnetization can be fully reversed with a current density of about 10^(4)A/cm^(2).The magnetization reversal is attributed to the combined effect of the out-of-plane magnetic field and the current-induced spin-orbital *** is found that the current-driven magnetization reversal is highly relevant to the temperature owing to the varied spin-orbital torque,and the current-driven magnetization reversal will be more efficient in low-temperature range,while the magnetic field is helpful for the magnetization reversal in high-temperature range.

关键词： critical current density magnetization reversal perpendicular magnetization hybrid driving

Electrically manipulating magnetization reversal via energy band engineering

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Science China(Physics,Mechanics & Astronomy) 2023年第5期66卷 181-187页

作者： Junwei Tong Yanzhao Wu Feifei Luo Fubo Tian Xianmin Zhang Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Material Science and EngineeringNortheastern UniversityShenyang 110819China Department of Physics Freie Universität BerlinBerlin 14195Germany State Key Laboratory of Superhard Materials College of PhysicsJilin UniversityChangchun 130012China

Realization of a magnetization reversal by an external electric field is vital for developing ultra-low-power spintronic *** this report,starting from energy band engineering,a general design principle is proposed for achieving electrical manipulation of a nonvolatile 180°magnetization reversal.A half semiconductor(HSC)and a bipolar magnetic semiconductor(BMS)are selected as the model of magnetic layers,whose conduction-band minimum and valence-band maximum are in the same and opposite spin states,*** on the analysis of virtual hopping and tight-binding models,the interlayer coupling of HSC/insulator/BMS devices is successfully tuned between ferromagnetic and antiferromagnetic interactions by varying electric field ***,the interlayer coupling nearly disappears after removing the electric field,proving the nonvolatile magnetization *** first-principles calculations,the feasibility of present design strategy is further confirmed by a representative device with the structure of CrBr3/h-BN/2H-VSe_(2).This design guideline and physical phenomena may open an avenue to explore magnetoelectric coupling mechanisms and develop next-generation spintronic devices.

关键词： magnetic semiconductor magnetization reversal energy band engineering

Current-induced synchronized magnetization reversal of two-body Stoner particles with dipolar interaction

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Chinese Physics B 2018年第6期27卷 434-442页

作者： Zhou-Zhou Sun Yu Yang J Schliemann College of Physics Optoelectronics and Energy Soochow University Suzhou 215006 China Institute for Theoretical Physics University of Regensburg D-93040 Regensburg Germany

We investigate magnetization reversal of two-body uniaxial Stoner particles, by injecting spin-polarized current through a spin-valve structure. The two-body Stoner particles perform synchronized dynamics and can act as an information bit in computer technology. In the presence of magnetic dipole–dipole interaction（DDI） between the two particles,the critical switching current Ic for reversing the two dipoles is analytically obtained and numerically verified in two typical geometric configurations. The Ic bifurcates at a critical DDI strength, where Ic can decrease to about 70% of the usual value without DDI. Moreover, we also numerically investigate the magnetic hysteresis loop, magnetization self-precession,reversal time and synchronization stability phase diagram for the two-body system in the synchronized dynamics regime.

关键词： magnetization reversal spin-polarized current Stoner particle

Effect of niobium addition on magnetization reversal behavior for SmCo-based magnets with TbCu7-type structure

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Journal of Rare Earths 2016年第1期34卷 61-65页

作者：胡晨宇泮敏翔吴琼葛洪良王秀敏卢阳春张朋越 Magnetism Key Laboratory of Zhejiang Province China Jiliang University Hangzhou 310018 China Zhejiang Kaiwen Magnetic Limited Company Dongyang 322105 China

The effect of Nb addition on the microstructure and magnetic properties of nanocrystaUine Sm（CobaiNbxZr0.02）7 permanent magnet were investigated, The magnetization reversal behavior for ball milled Sm（CobaiNbxZr0.02）7 samples with high coercivity was investigated by analyzing hysteresis curves and recoil loops of demagnetization curves. Nb addition proved to result in relevant improvement in the magnetic properties, especially in the coercivity He. It was shown that the magnetic properties of Sm（CobalNbx- Zr0.02）7 nanocrystalline magnets were improved by an additional 0.06 at.% Nb. In particular, Hc was improved from 602 to 786 kA/m at room temperature. The maximum value of the integrated recoil loops area for 0.06 at.% Nb-doped samples of 1.81 kJ/m3 was much lower than that of the Nb-free sample, which could be explained by a smaller recoverable portion of the magnetization remaining in the Nb-doped sample when the applied field was below the coercivity Hc. The nucleation field Hn for irreversible magnetization reversal of the magnetically hard phase were calculated by analyzed in terms of the△Mirrev-H curve and the Kondorsky model.

关键词： nanocrystalline magnet magnetization reversal YbCu7 structure magnetic property rare earths

Topology-like dynamical behavior of magnetization reversal in exchange-bias systems

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Chinese Physics B 2013年第7期22卷 503-506页

作者：苏垣昌张丽娟杨鑫潘靖胡经国 College of Physics Science and Technology Yangzhou University School of Physics and Technology Nanjing Normal University

In an exchange-bias system, the barriers with intrinsic potential energy may be asymmetric due to unidirectional anisotropy. Based on the Stoner–Wohlfarth model, we show that the asymmetric barriers may lead to four kinds of dynamical process underlying the hysteresis-loop measurement. These kinds of dynamical processes are different in a topology-like property, which can be controlled by the orientation of the external field. In our study, a new analysis approach has been proposed to reveal the dynamical behaviors of magnetization reversal. With this approach, coercivity, exchange-bias field, and asymmetry of hysteresis loops can be quantitatively obtained.

关键词： exchange-bias system intrinsic energy potential magnetization reversal

Statistical model of magnetization reversal in Nd-Fe-B sintered magnets

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Rare Metals 2006年第z1期25卷 521-525页

作者： WANG Huijie ZHU Minggang LI Wei ZHANG Xin Division of Functional Materials Central Iron & Steel Research Institute Beijing 100081 China Division of Functional Materials Central Iron & Steel Research Institute Beijing 100081 China Division of Functional Materials Central Iron & Steel Research Institute Beijing 100081 China China Petroleum Materials Tianjin Corporation Tianjin 300204 China

Statistical model of magnetization reversal was used to simulate the magnetization reversal behavior in the sintered Nd-Fe-B magnets with double grain-size distributions due to the abnormal grain growth (AGG). The magnetic properties and mechanical properties due to the formation of AGG grains in Nd-Fe-B sintered magnets were tested. The results show that the magnetic properties, especially the rectangularity were severely deteriorated after the formation of the AGG grains and a step was shown on the demagnetization curve, and the occurrence of AGG may account for the poor rectangularity and existence of the step on demagnetization curve according to the statistical model of magnetization reversal. The fracture toughness and bending strength are lowered because of the stress concentration in the AGG grains. The SEM images show that the formation of AGG grains is caused by the solid sintering due to the absence of RE-rich phase. Statistical model of magnetization reversal can qualitative by explain the dependence of the magnetization reversal behavior on the grain size in the Nd-Fe-B sintered magnets.

关键词： sintered Nd-Fe-B magnets mechanical properties magnetization reversal abnormal grain growth