论文标题
非均匀磁化重新定向对自旋轨道扭矩测量的影响
Influence of nonuniform magnetization reorientation on spin-orbit torque measurements
论文作者
论文摘要
铁磁性/非磁性多层中自旋轨道扭矩的测量通常是基于一个假设，即整个铁磁层均匀响应自旋轨道扭矩。当铁磁层的厚度与动态交换耦合长度相当时，该假设会分解，在某些测量几何形状中，该耦合长度可以短至几纳米。非均匀的磁化重新定向以及每个磁性子层对磁场的不均匀贡献，或者KERR效应可能会影响旋转轨道扭矩外推的准确性，特别是如果使用厚的铁磁层。在本文中，我们使用数值模型在三种不同的技术中研究了这种影响：磁极 - 凯尔效应方法，第二谐波方法和自旋扭矩铁磁共振方法。我们表明，第二次谐波和磁磁性kerr效应的方法容易受到非均匀磁化重新定向的影响，而自旋扭矩铁磁共振方法的影响要小得多。
Measurements of spin-orbit torques in a ferromagnetic/nonmagnetic multilayer are typically based on an assumption that the entire ferromagnetic layer uniformly responds to the spin-orbit torque. This assumption breaks down when the thickness of the ferromagnetic layer is comparable to the dynamic exchange coupling length, which can be as short as a few nanometers in certain measurement geometries. The nonuniform magnetization reorientation coupled with nonuniform contribution of each magnetic sublayer to the magnetoresistance or the Kerr effect may impact the accuracy in the extrapolation of spin-orbit torque, particularly if a thick ferromagnetic layer is used. In this paper, we use numerical models to investigate such an impact in three different techniques: the magneto-optic-Kerr-effect method, the second-harmonic method and the spin torque ferromagnetic resonance method. We show that the second-harmonic and magneto-optic-Kerr-effect methods are prone to be influenced by the nonuniform magnetization reorientation, while the spin torque ferromagnetic resonance method is much less impacted.
