激光激励下磁隧道结的热传导及自旋转移矩效应研究

Exploring and developing efficient way to manipulate spin, is not only an important part of fundamental research, but also a demand for further miniaturization of spintronic devices. This project is based on the interdisciplinary of heat, electron and spin, spincaloritronics, explores and studies the control of spin in magnetic tunnel junctions (MTJ) with the heat current or temperature gradient. The heat pulse is generated by the femtosecond laser pulse to produce a large temperature gradient through the MTJ. Using the temperature dependence of tunneling magnetoresistance, a time domain instantaneously temperature measurement technique is introduced, the finite element method is used to provide insight into the heat conduction process of heat pulse through MTJ. Using the Stoner-Wohlfarth magnetic model, the evolution of magnetic moment inversion in the free layer of MTJ on the temperature, current pulses and heat pulse is studied. The thermal spin transfer torque (T-STT) on the magnetic moment is clarified. The magnitude of the T-STT is experimentally evaluated and its dependence on the magnetic field angle is investigated. Finally, the conditions of spin precession and spin reversal with the effect is revealed in the micro-magnetic perspective and ultimately provide a basis for realization of the reading and writing of information in the MTJ with the T-STT effect.

探索和开发高效自旋控制方法，不仅是基础研究的重要内容，也是自旋电子元器件进一步小型化的需要。本项目基于热、电子与自旋的交叉学科，自旋热电子学，探索和研究利用热流或者温度梯度在磁隧道结(MTJ)中实现自旋控制的方法。采用飞秒激光脉冲产生的热脉冲，在MTJ中形成较大温度梯度；利用隧穿磁电阻与温度的依赖关系，引入时间域瞬时测量温度技术，并利用有限元法，模拟热脉冲在MTJ的传导过程，实验与模拟相结合获得各纳米层的热导率、层间热阻以及MTJ的温度梯度。利用Stoner-Wohlfarth磁学模型，研究温度、电流脉冲以及热脉冲下MTJ自由层磁矩反转的演化规律，阐明热激发的自旋转移矩效应(T-STT)对磁矩的调控机制，从实验上评估T-STT效应的量级，并揭示其对磁场角度的依赖关系，最后从微磁学角度揭示该效应实现自旋进动与自旋反转的条件，为最终实现利用T-STT效应在MTJ中实现信息读写提供依据。

在国家自然科学基金委员会的资助下，在课题组成员的共同努力下，项目 “：激光激励下磁隧道结的热传导及自旋转移矩效应研究”（No.11904343）按计划完成项目研究工作。本项目探索和研究了利用热流或者温度梯度在磁隧道结(MTJ)中实现自旋控制的方法。采用飞秒激光脉冲产生的热脉冲，在MTJ中形成较大温度梯度；利用隧穿磁电阻与温度的依赖关系，引入时间域瞬时测量温度技术，并利用有限元法，模拟热脉冲在MTJ的传导过程，实验与模拟相结合获得各纳米层的热导率、层间热阻以及MTJ中的温度梯度。利用Stoner-Wohlfarth磁学模型，研究了温度、电流脉冲以及热脉冲下MTJ自由层磁矩反转的演化规律，阐明了热激发的自旋转移矩效应(T-STT)对磁矩的调控机制，从实验上评估T-STT效应的量级，并揭示了其对磁场角度的依赖关系，最后从微磁学角度揭示该效应实现自旋进动与自旋反转的条件，为最终实现利用T-STT效应在MTJ中实现信息读写提供依据。基于本项目已发表文章9篇，其中9篇被SCI/EI收录；授权国家发明专利9项；项目成果获浙江省科技进步三等奖1项。