Transverse and Longitudinal Spin-Torque Ferromagnetic Resonance for Improved Measurement of Spin-Orbit Torque
Transverse and Longitudinal Spin-Torque Ferromagnetic Resonance for Improved Measurement of Spin-Orbit Torque
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DOI：
10.1103/physrevapplied.14.024024
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发表时间：
2020-08-11
影响因子：
4.6
通讯作者：
Ralph, Daniel C.
中科院分区：
文献类型：
--
作者：
Karimeddiny, Saba;Mittelstaedt, Joseph A.;Ralph, Daniel C.
自旋矩铁磁共振（ST-FMR）是测量重金属/铁磁体双层结构中自旋轨道矩（SOT）的常用方法。在测量过程中，其他共振过程，如自旋泵（SP）和加热，可以导致自旋电流或层之间的热流，通过反自旋霍尔效应（ISHE）和能斯特效应感应额外的共振电压信号。在标准ST-FMR几何结构中，这些额外伪影表现出对与来自SOT的整流信号相同的面内磁场的角度的依赖性。我们通过实验表明，整流和伪影电压可以通过测量横向于所施加电流的ST-FMR信号（即，在霍尔几何形状中）。我们发现，在Pt（6 nm）/Co 40 Fe 40 B20样品中，与薄于6 nm的Co 40 Fe 40 B20层的SOT整流信号相比，来自伪影的贡献很小，但对于较厚的磁性层可能很重要。我们观察到的伪影电压作为Co 40 Fe 40 B20厚度的函数，我们建议可能是由于共振加热效应和SP-ISHE贡献之间的竞争的符号变化。
Spin-torque ferromagnetic resonance (ST-FMR) is a common method used to measure spin-orbit torque (SOT) in heavy-metal/ferromagnet bilayer structures. In the course of a measurement, other resonant pro-cesses such as spin pumping (SP) and heating can cause spin-current or heat flows between the layers, inducing additional resonant voltage signals via the inverse spin Hall effect (ISHE) and Nernst effects. In the standard ST-FMR geometry, these extra artifacts exhibit a dependence on the angle of an in-plane magnetic field that is identical to the rectification signal from the SOT. We show experimentally that the rectification and artifact voltages can be quantified separately by measuring the ST-FMR signal transverse to the applied current (i.e., in a Hall geometry) in addition to the usual longitudinal geometry. We find that in Pt(6 nm)/Co40Fe40B20 samples the contribution from the artifacts is small compared with the SOT rectification signal for Co40Fe40B20 layers thinner than 6 nm, but can be significant for thicker magnetic layers. We observe a sign change in the artifact voltage as a function of the Co40Fe40B20 thickness that we suggest may be due to competition between a resonant heating effect and the SP-ISHE contribution.