摘要
非线性反铁磁材料表现出反常霍尔效应(AHE)、反常能斯特效应(ANE)等众多优异的物理性能,成为下一代室温自旋电子器件的重要候选材料,其中,具有420 K反铁磁转变温度的Mn_(3)Sn是最具代表性的材料之一。利用磁控溅射制备了非线性反铁磁Mn_(3)Sn多晶薄膜,薄膜表现出显著AHE,通过改变磁控溅射气压有效调控其矫顽场,室温最大值达到3.03×10^(5)A∙m^(-1),260 K时增加到5.73×10^(5)A∙m^(-1)。X射线粉末衍射和变温霍尔测试表明多晶Mn_(3)Sn薄膜中含有少量铁磁性Mn2Sn杂相,并导致AHE在大约250 K时反常霍尔系数由负号转变为正号;通过不同角度磁场和变温霍尔电阻测试,结合垂直各向异性铁磁薄膜霍尔电阻曲线,澄清了Mn_(3)Sn薄膜中AHE与其磁矩具有较小的关联,而主要源于动量空间非线性反铁磁自旋织构产生的非零贝利曲率。这些结果不仅为反铁磁Mn_(3)Sn中AHE的来源提供实验证据,而且为非线性反铁磁材料在未来高性能自旋电子器件中的应用打下基础。
The rapid development of information technology required spintronic devices with high storage density and low power con⁃sumption.Owing to no stray field,insensitivity to the external magnetic field,high precession frequency,and low damping coeffi⁃cient,antiferromagnetic materials were significant in the fabrication of next-generation spin storage and logic devices.Non-colinear an⁃tiferromagnetic materials such as Mn_(3)Sn and Mn3Ge exhibited novel physical phenomena that had never appeared in conventional anti⁃ferromagnetic materials.Among them,Mn_(3)Sn with a transition temperature of 420 K was one of the most representative materials.Here⁃in,direct current(DC)magnetron sputtering was used to grow antiferromagnetic Mn_(3)Sn film.The sputtering power was 30 W with sput⁃tering pressures of 2.5,3.0,3.5 and 4.0 Pa,respectively.The characterization results demonstrated that all the samples showed anti⁃ferromagnetic polycrystalline Mn_(3)Sn thin film with(0002)as the main orientation.The film contained a small amount of ferromagnetic Mn2Sn phase.The room-temperature anomalous Hall resistance curves of all our samples displayed negative anomalous Hall coeffi⁃cient,which met the anomalous Hall effect(AHE)characteristics of Mn_(3)Sn material.Maximum coercive field(3.03×10^(5)A·m^(-1))ap⁃peared in the sample deposited by the sputtering pressure of 3.0 Pa.When the temperature was reduced to 260 K,the coercive field reached 5.73×10^(5)A·m^(-1).The variations indicated that the coercive field of the Mn_(3)Sn film could be effectively controlled by optimizing the growth parameters of the film.The AHE of the Mn_(3)Sn film prepared with 3.0 Pa sputtering pressure was measured in the tempera⁃ture range of 50~350 K.The results suggested that the AHE above 250 K was negative,while the AHE below 250 K was positive.The anomalous Hall resistance curve near 250 K exhibited characteristics similar to the topological Hall effect.In combination with the structure and composition of the film,the reasons were as follows.The antiferromagnetic Mn_(3)Sn thin film contained a small amount of ferromagnetic Mn2Sn with Curie temperature around 250 K,which signified that it would turn into paramagnetic state above this tem⁃perature.Therefore,the anomalous Hall resistance was mainly the signal of antiferromagnetic Mn_(3)Sn and the anomalous Hall coeffi⁃cient was negative when the temperature was higher than 250 K.When the temperature was lower than 250 K,the magnetic moment of Mn2Sn gradually increased with the decrease of temperatures.As a result,Hall resistance that could induce positive anomalous Hall co⁃efficient gradually increased,which masked the AHE signal of Mn_(3)Sn and led to a positive anomalous Hall coefficient.When the tem⁃perature was close to the Curie temperature of ferromagnetic Mn2Sn(250 K),the magnetic moment of Mn2Sn was relatively small.Hence,its magnitude was comparable to AHE derived from the Mn_(3)Sn phase.The superposition of AHE with two different directions led to a curve similar to the topological Hall effect.The source of AHE in the non-colinear antiferromagnetic Mn_(3)Sn materials was relat⁃ed to non-zero Berry curvature in the momentum space of the non-colinear antiferromagnetic materials.These results not only provided experimental evidence for the source of AHE in antiferromagnetic Mn_(3)Sn,but also laid the foundation for the application of antiferro⁃magnetic materials in high-performance spintronic devices in the future.
作者
全志勇
陈翰韬
张伟
刘慧慧
许小红
Quan Zhiyong;Chen Hantao;Zhang Wei;Liu Huihui;Xu Xiaohong(School of Chemistry and Materials Science,Shanxi Normal University,Linfen 041004,China;Research Insti-tute of Materials Science,Shanxi Normal University,Linfen 041004,China;Key Laboratory of Magnetic Mole-cules and Magnetic Information Materials of Ministry of Education,Linfen 041004,China;Collaborative Innova-tion Center for Shanxi Advanced Permanent Magnetic Materials and Technology,Linfen 041004,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2021年第6期680-686,共7页
Chinese Journal of Rare Metals
基金
国家重点研发计划项目(2017YFB0405703)
国家自然科学基金项目(51571136)资助。
