Spin effects induced by thermal perturbation in a normal metal/magnetic insulator system

TL;DR

This paper investigates how thermal perturbations induce spin effects in a normal metal/magnetic insulator system, revealing the diffusive magnon behavior and relaxation processes responsible for spin pumping and spin-torque effects.

Contribution

It introduces a quantum nonequilibrium approach with effective temperatures for subsystems and derives generalized Bloch equations for spin-wave current propagation.

Findings

Magnon motion is diffusive in nature.

Magnon relaxation processes drive spin pumping.

Spin-torque effects are linked to magnon dynamics.

Abstract

Using one of the methods of quantum nonequilibrium statistical physics we have investigated the spin transport transverse to the normal metal/ferromagnetic insulator interface in hybrid nanostructures. An approximation of the effective parameters, when each of the interacting subsystems (electron spin, magnon, and phonon) is characterized by its own effective temperature have been considered. The generalized Bloch equations which describe the spin-wave current propagation in the dielectric have been derived. Finally, two sides of the spin transport "coin" have been revealed: the diffusive nature of the magnon motion and magnon relaxation processes, responsible for the spin pumping and the spin-torque effect.