Electronic Impurity Scattering Induced Spin Accumulation in Metallic Thin Films

TL;DR

This paper investigates how impurity scattering affects spin accumulation in metallic thin films using advanced theoretical methods, revealing the importance of impurity type and position, and aligning well with experimental data for platinum.

Contribution

It introduces a comprehensive theoretical framework combining Boltzmann and density functional theory to analyze impurity-induced spin accumulation, including vertex corrections and impurity effects.

Findings

Impurities at the surface enhance charge-to-spin conversion efficiency.

Anisotropic relaxation time approximation captures most effects in heavy metals.

Vertex corrections are significant in light metals.

Abstract

In order to explore the spin accumulation, evaluating the spin galvanic and spin Hall effect, we utilize the semi-classical Boltzmann equation based on input from the relativistic Korringa-Kohn-Rostoker Green's function method, within the density functional theory. We calculate the spin accumulation including multiple contributions, especially skew-scattering (scattering-in term) and compare this to three different approximations, which include the isotropic and anisotropic relaxation time approximation. For heavy metals, with strong intrinsic spin-orbit coupling, we find that almost all the effects are captured within the anisotropic relaxation time approximation. On the other hand, in light metals the contributions from the vertex corrections (scattering-in term) are comparable to the induced effect in anisotropic relaxation time approximation. We put a particular focus on the influence of the atomic character of the substitutional impurities on the spin accumulation as well as the dependence on the impurity position. As impurities will break space inversion symmetry of the thin film, this will give rise to both symmetric and antisymmetric contributions to the spin accumulation. In general, we find the impurities at the surface generate the largest efficiency of charge-to-spin conversion in case of the spin accumulation. Comparing our results to existing experimental findings for Pt we find a good agreement.