Dependence of spin pumping and spin transfer torque upon Ni 81 Fe 19 thickness in Ta / Ag / Ni 81 Fe 19 / Ag / Co 2 MnGe / Ag / Ta spin-valve structures
Dependence of spin pumping and spin transfer torque upon Ni 81 Fe 19 thickness in Ta / Ag / Ni 81 Fe 19 / Ag / Co 2 MnGe / Ag / Ta spin-valve structures
复制标题
Ta / Ag / Ni 81 Fe 19 / Ag / Co 2 MnGe / Ag / Ta 自旋阀结构中自旋泵浦和自旋转移扭矩对 Ni 81 Fe 19 厚度的依赖性
DOI：
10.1103/physrevb.96.144421
复制
发表时间：
2017
影响因子：
3.7
通讯作者：
Durrant C
中科院分区：
文献类型：
--
作者：
Durrant C
研究了Ta/Ag/(0-5 nm)/Ag(6 Nm)/(5 Nm)/Ag/Ta大面积自旋阀结构中的自旋泵浦，并探索了不同厚度的接收层的横向自旋电流吸收。在某些情况下，自旋电流吸收可以从矢量网络分析仪铁磁共振(VNA-FMR)实验中对源层阻尼的修改中推断出来。然而，自旋电流吸收是通过元素特定的相分辨X射线铁磁共振(XFMR)测量更准确地确定的，该测量直接探测作用于源层共振处的沉降层的自旋转移扭矩(STT)。通过与宏观自旋模型的比较，可以提取有效自旋混合电导的真实部分。我们发现外层Ta层的自旋电流吸收有显著的影响，而厚度小于0.6 nm的沉淀层在室温下是不连续的和超顺磁性的，并导致源层损耗显著增加。对于最厚的5 nm沉淀层，我们发现自旋电流吸收的增加与零频FMR线宽的减小相一致，这归因于界面质量的改善。研究表明，横向自旋电流吸收并不遵循普遍依赖于汇层厚度的规律，相反，汇层的结构质量起着至关重要的作用。
Spin pumping has been studied within Ta / Ag /(0–5 nm) / Ag (6 nm) /(5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption ofsink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of thesource layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfer torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. This study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.