Symmetry and magnitude of spin-orbit torques in ferromagnetic heterostructures
Symmetry and magnitude of spin-orbit torques in ferromagnetic heterostructures
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DOI：
10.1038/nnano.2013.145
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发表时间：
2013-08-01
影响因子：
38.3
通讯作者：
Gambardella, Pietro
中科院分区：
文献类型：
--
作者：
Garello, Kevin;Miron, Ioan Mihai;Gambardella, Pietro
最近的实验表明，在重金属/铁磁异质结构中，面内电流注入引起的磁化翻转引起了越来越多的关注，自旋扭矩的基础上的轨道到自旋动量转移。然而，自旋轨道力矩（SOTs）的对称性、大小和起源仍然是一个有争议的问题。在这里，我们报告的三维矢量测量的SOTs在AlOx/Co/Pt和MgO/CoFeB/Ta三层使用谐波分析的异常和平面霍尔效应。我们提供了一个通用的方案来测量作为磁化方向的函数的SOTs的幅度和方向。基于空间和时间反演对称性的参数，我们证明了重金属/铁磁层允许两个不同的SOTs具有奇数和偶数的行为相对于磁化反转。这样的扭矩包括强烈的各向异性类场和自旋转移类组件，这取决于重金属层的类型和退火处理。这些结果要求SOT模型，超越自旋霍尔和Rashba效应迄今为止的调查。
Recent demonstrations of magnetization switching induced by in-plane current injection in heavy metal/ferromagnetic heterostructures have drawn increasing attention to spin torques based on orbital-to-spin momentum transfer. The symmetry, magnitude and origin of spin-orbit torques (SOTs), however, remain a matter of debate. Here we report on the three-dimensional vector measurement of SOTs in AlOx/Co/Pt and MgO/CoFeB/Ta trilayers using harmonic analysis of the anomalous and planar Hall effects. We provide a general scheme to measure the amplitude and direction of SOTs as a function of the magnetization direction. Based on space and time inversion symmetry arguments, we demonstrate that heavy metal/ferromagnetic layers allow for two different SOTs having odd and even behaviour with respect to magnetization reversal. Such torques include strongly anisotropic field-like and spin transfer-like components, which depend on the type of heavy metal layer and annealing treatment. These results call for SOT models that go beyond the spin Hall and Rashba effects investigated thus far.