Spin relaxation and spin Hall transport in 5d transition-metal ultrathin films

TL;DR

This study investigates spin relaxation and spin Hall effects in 5d transition-metal ultrathin films, revealing significant anisotropy and shorter relaxation times compared to noble metals, with implications for spintronic applications.

Contribution

It provides the first comprehensive analysis of spin relaxation and spin Hall conductivity in 5d ultrathin films using relativistic first-principles calculations.

Findings

Spin-flip relaxation times are about hundreds of nanoseconds at 10 layers.

Anisotropy of relaxation rates can reach up to 97% due to Rashba surface states.

Spin Hall conductivity and angle are quantified for different 5d metals.

Abstract

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 which is one and two orders of magnitude shorter than that 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.