Spin relaxation and spin Hall transport in 5d transition-metal ultrathin films
Spin relaxation and spin Hall transport in 5d transition-metal ultrathin films
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DOI：
10.1103/physrevb.90.064406
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发表时间：
2014-05
影响因子：
3.7
通讯作者：
N. H. Long;P. Mavropoulos;B. Zimmermann;D. Bauer;S. Blugel;Y. Mokrousov
中科院分区：
文献类型：
--
作者：
N. H. Long;P. Mavropoulos;B. Zimmermann;D. Bauer;S. Blugel;Y. Mokrousov
研究了以自杂原子杂质为散射体的5d$过渡金属超薄膜中由Elliott-Yafet机制引起的自旋弛豫和由偏散射引起的外源自旋霍尔电导率。Elliott- yafet参数值和自旋翻转弛豫速率值显示出与Elliott近似一致的相互关系。在10层厚度下，5d过渡金属薄膜的自旋翻转弛豫时间约为几百纳秒。该时间尺度比Au薄膜和Cu薄膜的时间尺度分别短一个数量级和两个数量级。分析了Elliott-Yafet参数和自旋翻转弛豫速率相对于自旋量化轴方向的各向异性效应以及相对于结晶轴的各向异性效应。我们发现，由于费米表面的Rashba表面态，自旋翻转弛豫率的各向异性得到了增强，在10层Hf（0001）薄膜中达到97%，在10层W（110）薄膜中达到71%。最后，利用玻尔兹曼方法计算了自旋霍尔电导率和自旋霍尔角。我们的计算采用第一原理全势Korringa-Kohn-Rostoker格林函数方法的相对论版本。
The spin relaxation induced by the Elliott-Yafet mechanism and the extrinsic spin Hall conductivity due to the skew scattering are investigated in $5d$ transition-metal ultrathin films with self-adatom impurities as scatterers. The values of the Elliott-Yafet parameter and of the spin-flip relaxation rate reveal a correlation with each other that is in agreement with the Elliott approximation. At 10-layer thickness, the spin-flip relaxation time in $5d$ transition-metal films is quantitatively reported about few hundred nanoseconds at atomic percent. This time scale is one and two orders of magnitude shorter than the values in Au and Cu thin films, respectively. The anisotropy effect of the Elliott-Yafet parameter and of the spin-flip relaxation rate with respect to the direction of the spin-quantization axis in relation to the crystallographic axes is also analyzed. We find that the anisotropy of the spin-flip relaxation rate is enhanced due to the Rashba surface states on the Fermi surface, reaching values as high as 97% in 10-layer Hf(0001) film or 71% in 10-layer W(110) film. Finally, the spin Hall conductivity as well as the spin Hall angle due to the skew scattering off self-adatom impurities are calculated using the Boltzmann approach. Our calculations employ a relativistic version of the first-principles full-potential Korringa-Kohn-Rostoker Green function method.