Spin-memory loss induced by bulk spin-orbit coupling at ferromagnet/heavy-metal interfaces

TL;DR

This paper introduces a new mechanism where bulk spin-orbit coupling in heavy metals causes significant spin-flip at ferromagnet/heavy-metal interfaces, leading to spin-memory loss, especially near band crossing points.

Contribution

The study proposes a novel bulk spin-orbit coupling mechanism for spin-memory loss, emphasizing the role of atomic orbital degrees of freedom and spin-orbital entanglement.

Findings

Bulk spin-orbit coupling induces spin-flip at interfaces.

Strong spin-memory loss occurs near band crossing points.

Mechanism is effective even with weak interfacial spin-orbit coupling.

Abstract

A spin current through a ferromagnet/heavy-metal interface may shrink due to the spin-flip at the interface, resulting in the spin-memory loss. Here we propose a mechanism of the spin-memory loss. In contrast to other mechanisms based on interfacial spin-orbit coupling, our mechanism is based on the bulk spin-orbit coupling in a heavy-metal. We demonstrate that the bulk spin-orbit coupling induces the entanglement between the spin and orbital degrees of freedom and this spin-orbital entanglement can give rise to sizable spin-flip at the interface even when the interfacial spin-orbit coupling is weak. Our mechanism emphasizes crucial roles of the atomic orbital degree of freedom and induces the strong spin-memory loss near band crossing points between bands of different orbital characters.