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Ambi-chiral anomalous hall effect in magnetically doped topological insulators

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Science China(Physics,Mechanics & Astronomy) 2022年第6期65卷 116-122页

作者： Chang Liu YunYi Zang Yan Gong Ke He XuCun Ma QiKun Xue YaYu Wang State Key Laboratory of Low Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China Beijing Academy of Quantum Information Sciences Beijing 100193China Frontier Science Center for Quantum Information Beijing 100084China

The chirality associated with broken time-reversal symmetry in magnetically doped topological insulators has important implications for the quantum transport phenomena.Here we report anomalous hall effect studies in Mn-and Cr-doped Bi_(2)Te_(3) topological insulators with varied thicknesses and doping contents.By tracing the magnitude of the anomalous hall resistivity,we find that the Mn-type anomalous hall effect characterized with clockwise chirality is strengthened by the reduction of film thickness,which is opposite to that of the Cr-type anomalous hall effect with counterclockwise chirality.We provide a phenomenological physical picture to explain the evolution of the magnetic order and the anomalous hall chirality in magnetically doped topological insulators.

关键词： topological insulator anomalous hall effect chirality magnetic order

anomalous hall effect in ferromagnetic LaCo_(2)As_(2) and ferrimagnetic NdCo_(2)As_(2)

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中国物理B:英文版 2023年第10期32卷 641-648页

作者：黄雨晴郑鹏宇刘瑞许锡童吴紫阳董超王俊峰殷志平贾爽 International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100081China Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory Xianhu Hydrogen ValleyFoshan 528200China Department of Physics and Center for Advanced Quantum Studies Beijing Normal UniversityBeijing 100875China Wuhan National High Magnetic Field Center and School of Physics Huazhong University of Science and TechnologyWuhan 430074China Kunshan Innovation Institute of Nanjing University Kunshan 215347China

We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous hall effect(AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo_(2)As_(2) manifests pronounced sign reversal and multiple hysteresis loops in temperature-and field-dependent magnetization, hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo_(2)As_(2) is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the hall effect on the details of the magnetic structures in ferrimagnetic NdCo_(2)As_(2) provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.

关键词： anomalous hall effect ferrimagnetism magnetic compensation meta-magnetic transitions

anomalous hall effect in ferromagnetic Weyl semimetal candidate Zr1-x VxCo1.6Sn

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Chinese Physics B 2020年第7期29卷 204-210页

作者：王光强孙彰昊司鑫宇贾爽 International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Collaborative Innovation Center of Quantum Matter Beijing 100871China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China Beijing Academy of Quantum Information Sciences Beijing 100193

We grew single crystals of vanadium-substituted,ferromagnetic Weyl semimetal candidate Zr1-xVxCo1.6Sn from molten tin flux.These solid solutions all crystallize in a full Heusler structure(L21)while their Curie temperatures and magnetic moments are enhanced by V-substitution.Their resistivity gradually changes from bad-metal-like to semiconductor-like with increasing x while the anomalous hall effect(AHE),which can be well fitted by Tian-Ye-Jin(TYJ)scaling,[1]is also enhanced.Moreover,we find an apparent electron-electron interaction(EEI)induced quantum correction in resistivity at low temperature.The anomalous hall conductivity(AHC)dominated by the intrinsic term is not corrected.

关键词： anomalous hall effect ferromagnetic Weyl semimetal full Heusler electron-electron interaction

anomalous hall effect of facing-target sputtered ferrimagnetic Mn_(4)N epitaxial films with perpendicular magnetic anisotropy

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Chinese Physics B 2022年第4期31卷 653-659页

作者：张泽宇张强米文博 Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparation Technology School of ScienceTianjin UniversityTianjin 300354China Core Technology Platforms New York University Abu DhabiP.O.Box 129188Abu DhabiUnited Arab Emirates

Epitaxial Mn_(4)N films with different thicknesses were fabricated by facing-target reactive sputtering and their anomalous hall effect(AHE)is investigated systematically.The hall resistivity shows a reversed magnetic hysteresis loop with the magnetic field.The magnitude of the anomalous hall resistivity sharply decreases with decreasing temperature from300 K to 150 K.The AHE scaling law in Mn_(4)N films is influenced by the temperature-dependent magnetization,carrier concentration and interfacial scattering.Different scaling laws are used to distinguish the various contributions of AHE mechanisms.The scaling exponentγ>2 for the conventional scaling in Mn_(4)N films could be attributed to the residual resistivityρ_(xx0).The longitudinal conductivityσ_(xx)falls into the dirty regime.The scaling ofρ_(AH)=αρ_(xx0)+bρ_(xx)~nis used to separate out the temperature-independentρ_(xx0)from extrinsic contribution.Moreover,the relationship betweenρ_(AH)and pxx is fitted by the proper scaling to clarify the contributions from extrinsic and intrinsic mechanisms of AHE,which demonstrates that the dominant mechanism of AHE in the Mn4 N films can be ascribed to the competition between skew scattering,side jump and the intrinsic mechanisms.

关键词： Mn_(4)N epitaxial film anomalous hall effect scaling law

anomalous hall effect in perpendicular CoFeB thin films

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Chinese Physics B 2014年第4期23卷 9-17页

作者：朱涛 Institute of Physics and Beijing National Laboratory for Condensed Matter Physics Chinese Academy of Sciences

Our recent research achievements in the perpendicular magnetic anisotropy （PMA） properties of the CoFeB sand- wiched by MgO and tantalum layers are summarized. We found that the PMA behaviors of Ta/CoFeB/MgO and MgO/CoFeB/Ta thin films are different. The larger PMA in the latter film is related to the lower magnetization of CoFeB deposited on MgO. Furthermore, we have demonstrated a large anomalous hall effect in perpendicular CoFeB thin fihn. Our results show large anomalous hall resistivity, large longitudinal resistivity, and low switching field can be achieved, all at the same time, in the perpendicular CoFeB thin film. anomalous hall effect with high and linear sensitivity is also found in an MgO/CoFeBFFa thin film with a thick MgO layer, which opens a door tbr future device applications of perpendicular ferromagnetic thin films.

关键词： anomalous hall effect perpendicular magnetic anisotropy magnetic properties of interfaces

Nonmonotonic anomalous hall effect and anisotropic magnetoresistance in SrRuO_(3)/PbZr_(0.52)Ti_(0.48)O_(3)heterostructures

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Chinese Physics B 2023年第10期32卷 592-599页

作者：王振礼康朝阳贾彩虹郭海中张伟风 Center for Topological Functional Materials Henan UniversityKaifeng 475004China Key Laboratory of Material Physics School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China

We fabricate SrRuO_(3)/PbZr_(0.52)Ti_(0.48)O_(3)heterostructures each with an in-plane tensile-strained SrRuO_(3)layer and investigate the effect of an applied electric field on anomalous hall effect.The four-fold symmetry of anisotropic magnetoresistance and the nonmonotonic variation of anomalous hall resistivity are observed.By applying positive electric field or negative electric field,the intersecting hump-like feature is suppressed or enhanced,respectively.The sign and magnitude of the anomalous hall conductivity can be effectively controlled with an electric field under a high magnetic field.The electric-field-modulated anomalous hall effect is associated with the magnetization rotation in SrRuO_(3).The experimental results are helpful in modulating the magnetization rotation in spintronic devices based on SrRuO_(3)heterostructures.

关键词： Berry curvature electric field anomalous hall effect anisotropic magnetoresistance magnetization rotation

Characteristics of anomalous hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic,extrinsic,and external electric-field induced spin-orbit couplings

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Chinese Physics B 2012年第2期21卷 469-476页

作者：刘宋颜玉珍胡梁宾 Laboratory of Quantum Information Technology School of Physics and Telecommunication EngineeringSouth China Normal UniversityGuangzhou 510631China

The various competing contributions to the anomalous hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic, extrinsic and external electric-field induced spin-orbit coupling were investigated theoretically. Based on a unified semiclassical theoretical approach, it is shown that the total anomalous hall conductivity can be expressed as the sum of three distinct contributions in the presence of these competing spin-orbit interactions, namely an intrinsic contribution determined by the Berry curvature in the momentum space, an extrinsic contribution determined by the modified Bloch band group velocity and an extrinsic contribution determined by spin-orbit-dependent impurity scattering. The characteristics of these competing contributions are discussed in detail in the paper.

关键词： anomalous hall effect intrinsic spin orbit coupling extrinsic spin orbit coupling exter- nal electric-field induced spin-orbit coupling

Room-temperature anomalous hall effect and magnetroresistance in(Ga,Co)-codoped ZnO diluted magnetic semiconductor films

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Chinese Physics B 2011年第3期20卷 420-425页

作者：刘学超陈之战施尔畏廖达前周克谨 Shanghai Institute of Ceramics Chinese Academy of Sciences Department of Physics The University of WarwickCoventryCV4 7AL Swiss Light Source Paul Scherrer Institut5232 Villigen PSISwitzerland

This paper reports that the （Ga, Co）-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition. Room-temperature ferromagnetism is observed for the as-grown thin films. The x-ray absorption fine structure characterization reveals that Co2＋ and Ga3＋ ions substitute for Zn2＋ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin. The ferromagnetic （Ga, Co）-codoped ZnO thin films exhibit carrier concentration dependent anomalous hall effect and positive magnetoresistance at room tempera- ture. The mechanism of anomalous hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.

关键词： diluted magnetic semiconductors （Ga Co）-codoped ZnO anomalous hall effect magnetroresisance

Doping tuned anomalous hall effect in the van der Waals magnetic topological phases Mn(Sb_(1-x)Bi_(x))_(4)Te_(7)

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中国物理B:英文版 2023年第9期32卷 422-426页

作者：张鑫江志诚袁健侯骁飞王霞余娜邹志强刘正太夏威于振海沈大伟郭艳峰 School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050China Analytical Instrumentation Center School of Physical Science and TechnologyShanghaiTech UniversityShanghai 201210China National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China ShanghaiTech Laboratory for Topological Physics ShanghaiTech UniversityShanghai 201210China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

The van der Waals(vdW)MnSb4Te7is a newly synthesized antiferromagnetic(AFM)topological insulator hosting a robust axion insulator state irrelative to the specific spin structure.However,the intrinsic hole doped character of MnSb_4Te_7makes the Fermi level far away from the Dirac point of about 180 meV,which is unfavorable for the exploration of exotic topological properties such as the quantum anomalous hall effect(QAHE).To shift up the Fermi level close to the Dirac point,the strategy of partially replacing Sb with Bi as Mn(Sb_(1-x)Bi_(x))_(4)Te_(7)was tried and the magnetotransport properties,in particular,the anomalous hall effect,were measured and analyzed.Through the electron doping,the anomalous hall conductanceσAH changes from negative to positive between x=0.3 and 0.5,indicative of a possible topological transition.Besides,a charge neutrality point(CNP)also appears between x=0.6 and 0.7.The results would be instructive for further understanding the interplay between nontrivial topological states and the magnetism,as well as for the exploration of exotic topological properties.

关键词： anomalous hall effect doping topological materials