Investigation of spin orbit torque driven dynamics in ferromagnetic heterostructures
Investigation of spin orbit torque driven dynamics in ferromagnetic heterostructures
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DOI：
10.1016/j.jmmm.2019.166211
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发表时间：
2019-10
影响因子：
2.7
通讯作者：
Xinran Zhou;Hang Chen;Y. Ou;Tao Wang;Rasoul Barri;Harsha Kannan;J. Xiao;M. Doty
中科院分区：
文献类型：
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作者：
Xinran Zhou;Hang Chen;Y. Ou;Tao Wang;Rasoul Barri;Harsha Kannan;J. Xiao;M. Doty
我们使用基于极磁光克尔效应 (MOKE) 的时间分辨 (TR) 测量来研究 Py（坡莫合金）/Pt 和 Ta/CoFeB 双层中自旋轨道扭矩激发的磁化动力学。分析表明，类场（FL）自旋轨道扭矩（SOT）主导磁化进动第一个振荡周期的振幅，类阻尼（DL）扭矩决定最终的稳态磁化强度。在我们的双层样品中，我们从时间分辨磁化振荡谱中提取了两个 SOT 的有效场 hFL 和 hDL。提取的值与从时间积分 DCMOKE 测量中提取的值非常一致，表明 SOT 在高频下不会发生变化。我们还发现，第一次振荡与稳态的振幅比与 hFL/hDL 比率成线性比例。第一振荡幅度与沿电流方向施加的外场成反比，而稳态值与之无关。
We use time-resolved (TR) measurements based on the polar magneto-optical Kerr effect (MOKE) to study the magnetization dynamics excited by spin orbit torques in Py (Permalloy)/Pt and Ta/CoFeB bilayers. The analysis reveals that the field-like (FL) spin orbit torque (SOT) dominates the amplitude of the first oscillation cycle of the magnetization precession and the damping-like (DL) torque determines the final steady-state magnetization. In our bilayer samples, we have extracted the effective fields,hFLandhDL, of the two SOTs from the time-resolved magnetization oscillation spectrum. The extracted values are in good agreement with those extracted from time-integrated DCMOKE measurements, suggesting that the SOTs do not change at high frequencies. We also find that the amplitude ratio of the first oscillation to steady state is linearly proportional to the ratiohFL/hDL. The first oscillation amplitude is inversely proportional to, whereas the steady state value is independent of, the applied external field along the current direction.