Institute of Physics, Johannes Gutenberg-University Mainz , 55099 Mainz, Germany.
Graduate School of Excellence Materials Science in Mainz , 55128 Mainz, Germany.
Nano Lett. 2018 Feb 14;18(2):1064-1069. doi: 10.1021/acs.nanolett.7b04538. Epub 2018 Feb 2.
We measure the inverse spin Hall effect of CuIr thin films on yttrium iron garnet over a wide range of Ir concentrations (0.05 ⩽ x ⩽ 0.7). Spin currents are triggered through the spin Seebeck effect, either by a continuous (dc) temperature gradient or by ultrafast optical heating of the metal layer. The spin Hall current is detected by electrical contacts or measurement of the emitted terahertz radiation. With both approaches, we reveal the same Ir concentration dependence that follows a novel complex, nonmonotonous behavior as compared to previous studies. For small Ir concentrations a signal minimum is observed, whereas a pronounced maximum appears near the equiatomic composition. We identify this behavior as originating from the interplay of different spin Hall mechanisms as well as a concentration-dependent variation of the integrated spin current density in CuIr. The coinciding results obtained for dc and ultrafast stimuli provide further support that the spin Seebeck effect extends to terahertz frequencies, thus enabling a transfer of established spintronic measurement schemes into the terahertz regime. Our findings also show that the studied material allows for efficient spin-to-charge conversion even on ultrafast time scales.
我们在很宽的 Ir 浓度范围内（0.05 ⩽ x ⩽ 0.7）测量了 CuIr 薄膜在钇铁石榴石上的反自旋霍尔效应。通过自旋塞贝克效应，无论是通过连续（dc）温度梯度还是通过金属层的超快光学加热，都可以产生自旋电流。自旋霍尔电流通过电接触或发射太赫兹辐射的测量来检测。通过这两种方法，我们都揭示了相同的 Ir 浓度依赖性，与之前的研究相比，这种依赖性呈现出一种新颖的复杂、非单调的行为。对于较小的 Ir 浓度，观察到信号最小值，而在等原子组成附近出现明显的最大值。我们将这种行为归因于不同的自旋霍尔机制的相互作用以及 CuIr 中积分自旋电流密度的浓度依赖性变化。直流和超快刺激获得的一致结果进一步证明了自旋塞贝克效应扩展到太赫兹频率，从而使成熟的自旋电子测量方案能够转移到太赫兹区域。我们的研究结果还表明，即使在超快时间尺度上，所研究的材料也允许高效的自旋到电荷转换。
