Spin Pumping and Spin Transfer

TL;DR

This paper demonstrates the fundamental equivalence of spin pumping and spin transfer torques in magnetic structures, supported by theoretical proofs, first-principles calculations, and experimental validation.

Contribution

It establishes the reciprocal relationship between spin pumping and spin transfer torques using Onsager's relations and reviews their theory in various magnetic structures.

Findings

Spin pumping and spin transfer are fundamentally equivalent processes.

First-principles calculations of damping parameters match experimental data.

Theoretical and experimental results show good agreement.

Abstract

Spin pumping is the emission of a spin current by a magnetization dynamics while spin transfer stands for the excitation of magnetization by spin currents. Using Onsager's reciprocity relations we prove that spin pumping and spin-transfer torques are two fundamentally equivalent dynamic processes in magnetic structures with itinerant electrons. We review the theory of the coupled motion of the magnetization order parameter and electron for textured bulk ferromagnets (e.g. containing domain walls) and heterostructures (such as spin valves). We present first-principles calculations for the material-dependent damping parameters of magnetic alloys. Theoretical and experimental results agree in general well.