基于反铁磁的无外场辅助自旋轨道矩磁隧道结模型分析  

Analysis of spin-orbit torque magnetic tunnel junction model without external magnetic field assistance based on antiferromagnetism

作　　者：王可欣 粟傈 童良乐 Wang Ke-Xin;Su Li;Tong Liang-Le(Information Engineering College,Capital Normal University,Beijing 100048,China)

机构地区：[1]首都师范大学信息工程学院,北京100048

出　　处：《物理学报》2023年第19期299-308,共10页Acta Physica Sinica

基　　金：北京市自然科学基金(批准号:4194073);北京市科技计划(批准号:KM202110028010);北京市优秀人才培养资助青年骨干个人项目(批准号:2018000020124G124)资助的课题。

摘　　要：自旋轨道转矩(spin-orbit torque,SOT)为超低功耗自旋电子器件提供新的实现方法,在反铁磁材料体系中面内交换偏置场可辅助SOT磁化翻转,同时利用电压调控磁各向异性(voltage-controlled magnetic anisotropy,VCMA)能有效降低翻转势垒,从而实现无外场辅助的磁隧道结.本文通过求解修正LandauLifshitz-Gilbert(LLG)方程,建立反铁磁/铁磁/氧化物构成的无外场辅助自旋轨道矩的磁隧道结模型,并对其磁化动力学过程进行分析.以IrMn/CoFeB/MgO材料体系为例,揭示了影响磁化翻转的因素,包括交换偏置(exchange bias,EB)效应对临界翻转电流ISOT的影响,VCMA效应和SOT类场转矩的影响机制;分析了实际应用中磁隧道结制作工艺偏差的影响.结果表明:EB效应与VCMA效应共同作用能极大降低临界翻转电流ISOT,从而实现完全无场开关切换;SOT类场转矩对磁化翻转起主导作用,且一定条件下可实现器件在ps量级的无场翻转;以及当氧化层厚度偏差γtf?10%或自由层厚度偏差γtox?13%时MTJ能实现有效切换.基于反铁磁的无场辅助自旋轨道矩器件将为新一代超低功耗、超高速度和超高集成度器件和电路提供极具前景的解决方案.HEB tf⩽10%tox⩽13%The effect of spin-orbit torque(SOT)provides a new method of implementing ultra-low power spintronic devices.The in-plane exchange bias(EB)field in antiferromagnetic material can effectively assist SOT magnetization switching.Meanwhile,the utilization of voltage-controlled magnetic anisotropy(VCMA)can effectively reduce the switching barrier.Taking advantage of the EB and VCMA effect,it is possible to realize SOT magnetic tunnel junctions without external field assistance.In this work,a spin-orbit torque magnetic tunnel junction model composed of antiferromagnetic/ferromagnetism/oxides without external magnetic field is developed by solving the modified Landau-Lifshitz-Gilbert(LLG)modular equation,and its magnetization dynamics is analyzed and studied.The effective fields in the model include the demagnetization field,thermal noise field,perpendicular magnetic anisotropy field with VCMA effect,and exchange bias field.Taking IrMn/CoFeB/MgO material system for example,the factors affecting the precession of magnetization are investigated,such as the effect of the exchange bias field,the VCMA effect and the mechanism of SOT field-like torque.Considering the practical applications,the effect of the deviation of the fabrication process of magnetic tunnel junctions is also analyzed.The simulation results demonstrate that the combined effect of with VCMA effect can greatly reduce the critical ISOT,thus assisting and realizing the complete field-free magnetization reversal;the SOT field-like torque plays a dominant role in realizing the magnetization reversal,and by adjusting the ratio of the SOT field-like torque to the damping-like torque,field free switching can be realized in the device at the ps grade;and the MTJ can realize effective switching when the deviation of oxide thickness or the deviation of free layer thickness.Spin-orbit torque devices based on the antiferromagnetic without external magnetic field will provide highly promising solutions for a new-generation ultra-low power,ultra-high

关 键 词：自旋轨道矩磁隧道结 压控磁各向异性 交换偏置 工艺偏差 

分 类 号：O469[理学—凝聚态物理]