Time-resolved measurement of spin-transfer-driven ferromagnetic resonance and spin torque in magnetic tunnel junctions
Time-resolved measurement of spin-transfer-driven ferromagnetic resonance and spin torque in magnetic tunnel junctions
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DOI：
10.1038/nphys1928
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发表时间：
2011-06-01
期刊：
影响因子：
19.6
通讯作者：
Ralph, Daniel C.
中科院分区：
文献类型：
--
作者：
Wang, Chen;Cui, Yong-Tao;Ralph, Daniel C.
自旋极化电流对铁磁元件施加的转矩的偏置依赖性对于理解磁性器件中的基本自旋物理学及其应用是重要的。近年来引入了几种实验技术来测量磁隧道结中的自旋传递转矩。然而，这些技术只提供了扭矩的间接测量，其关于偏置依赖性的结果在定性和定量上都不一致。在这里，我们证明了磁隧道结中的自旋扭矩可以通过使用时域技术来检测响应于振荡自旋扭矩的共振磁进动直接测量。该技术在与应用相关的高偏置范围内是准确的，并且由于它直接检测由自旋扭矩引起的小角度线性响应磁动力学，因此相对不受影响竞争技术的人工制品的影响。在高偏置下，我们发现自旋力矩矢量与通常假设的简单的最低阶泰勒级数近似明显不同。
The bias dependence of the torque that a spin-polarized current exerts on ferromagnetic elements is important for understanding fundamental spin physics in magnetic devices and for applications. Several experimental techniques have been introduced in recent years in attempts to measure spin-transfer torque in magnetic tunnel junctions. However, these techniques have provided only indirect measures of the torque and their results regarding bias dependence are qualitatively and quantitatively inconsistent. Here we demonstrate that spin torque in magnetic tunnel junctions can be measured directly by using time-domain techniques to detect resonant magnetic precession in response to an oscillating spin torque. The technique is accurate in the high-bias regime relevant for applications, and because it detects directly small-angle linear-response magnetic dynamics caused by spin torque it is relatively immune to artefacts affecting competing techniques. At high bias we find that the spin-torque vector differs markedly from the simple lowest-order Taylor series approximations commonly assumed.