Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films

TL;DR

This study reveals how surface asymmetry in supported metallic films causes strong spin-orbit fields and rapid spin dephasing through the Dyakonov-Perel mechanism, with implications for spintronics.

Contribution

It provides a quantitative analysis of spin dephasing in metallic films due to surface asymmetry and spin-orbit interactions using density functional calculations.

Findings

Surface asymmetry induces strong spin-orbit fields.

Spin dephasing is oscillatory with a rapid initial decay.

Persistent spin signals last much longer due to spin traps.

Abstract

Spin dephasing by the Dyakonov-Perel mechanism in metallic films deposited on insulating substrates is revealed, and quantitatively examined by means of density functional calculations combined with a kinetic equation. The surface-to-substrate asymmetry, probed by the metal wave functions in thin films, is found to produce strong spin-orbit fields and a fast Larmor precession, giving a dominant contribution to spin decay over the Elliott-Yafet spin relaxation up to a thickness of 70 nm. The spin dephasing is oscillatory in time with a rapid (sub-picosecond) initial decay. However, parts of the Fermi surface act as spin traps, causing a persistent tail signal lasting 1000 times longer than the initial decay time. It is also found that the decay depends on the direction of the initial spin polarization, resulting in a spin-dephasing anisotropy of 200% in the examined cases.