Spin transfer torque dynamics in diluted ferromagnetic semiconductor nanostructures

本课题研究了GaMnAs稀释铁磁半导体纳米结构中的超快速自旋传递转矩（STT）磁化动力学。利用基于GaMnAs的磁隧道势垒（MTJ）纳米柱中的高密度电流诱导STT磁化进动。通过对低温下纳米柱隧穿磁电阻（TMR）的宽带宽时间和频率分辨测量来检测进动动力学。STT进动频率和线宽作为外部参数（STT电流密度、静场角度和振幅等）的函数的参数依赖性将使我们对GaMnAs隧道系统中STT的性质有一个详细的了解，并将允许区分STT的可能矢量分量。用时间分辨磁输运方法研究STT诱导的大角度进动。在此基础上，将设计并测试优化的超快速STT磁化反转方案。该项目将深入了解伽玛纳纳米器件的超快速STT磁化动力学和磁化反转。从而为未来超快速DMS自旋电子器件和应用的发展提供了基础。

In this project the ultra fast spin transfer torque (STT) magnetization dynamics in GaMnAs diluted ferromagnetic semiconductor nanostructures are investigated. High density currents in GaMnAs based magnetic tunnel barrier (MTJ) nanopillars are used to induce STT magnetization precession. The precessional dynamics are detected by wide bandwidth time and frequency resolved measurements of the tunneling magneto resistance (TMR) of the nanopillars at cryogenic temperatures. The parameter dependence of the STT precession frequency and linewidth as function of external parameters (STT current density, static field angle and amplitude,…) will yield a detailed insight into the nature of STT in GaMnAs tunnel systems and will allow to distinguish possible vector components of STT. STT induced large angle precession will be studied by time resolved magneto transport. Based on this, optimized ultra fast STT magnetization reversal schemes will be devised and tested. This project will allow a deep insight into ultra fast STT magnetization dynamics and magnetization reversal of GaMnAs nanodevices. It thus provides the basis for the development of future ultra fast DMS based spintronic devices and applications.