Spin relaxation and the Elliott-Yafet parameter in W(001) ultrathin films: surface states, anisotropy and oscillation effects

TL;DR

This paper uses first-principles calculations to study spin relaxation in ultrathin W(001) films, revealing oscillatory behavior, surface state effects, and anisotropy in relaxation rates related to film thickness and spin polarization direction.

Contribution

It provides a detailed first-principles analysis of spin relaxation mechanisms, including surface states and anisotropy, in ultrathin tungsten films, highlighting the oscillatory and directional dependence of relaxation rates.

Findings

Spin-mixing parameter oscillates with film thickness.

Surface states and Rashba effect influence spin relaxation.

Spin-relaxation rate varies by up to 47% with polarization direction.

Abstract

Using first-principles methods based on density-functional theory we investigate the spin relaxation in W(001) ultrathin films. Within the framework of the Elliott-Yafet theory we calculate the spin mixing of the Bloch states and we explicitly consider spin-flip scattering off self-adatoms. We find an oscillatory behavior of the spin-mixing parameter and relaxation rate as a function of the film thickness, which we trace back tosurface-state properties. We also analyze the Rashba effect experienced by the surface states and discuss its influence on the spin relaxation. Finally we calculate the anisotropy of the spin-relaxation rate with respect to the polarization direction of the excited spin population relative to the crystallographic axes of thefilm. We find that the spin-relaxation rate can increase by as much as 47% when the spin polarization is directed out of plane, compared to the case when it is in plane. Our calculations are based on the multiple-scattering formalism of the Korringa-Kohn-Rostoker Green-function method.