Unified formulation of interfacial magnonic pumping from non-collinear magnets

TL;DR

This paper presents a comprehensive theoretical framework for understanding how magnons generate spin currents at interfaces with non-collinear magnetic configurations, applicable to various experimental setups like spin Seebeck and spin pumping.

Contribution

It introduces a unified formulation for interfacial magnonic spin pumping in non-collinear magnets, encompassing different non-equilibrium driving mechanisms and topological effects.

Findings

Derived a general formula for magnonic spin current at interfaces.

Applied the theory to a honeycomb topological ferromagnet.

Identified the role of topological edge magnons in spin pumping.

Abstract

We establish a general formulation for spin current pumped by magnons at the interface between a normal metal and a magnetic insulator, valid for any non-collinear magnetic configuration in the linear spin wave regime. This current is generated by driving the system in a non-equilibrium state, covering setups such as thermal spin injection (spin Seebeck effect) or spin voltage by irradiation of the insulator (spin pumping). We illustrate the formula in the special case of a honeycomb topological ferromagnet, for simplicity, and cover both the spin Seebeck and spin-pumping setups. We show how the topological parameters influence the spin current and propose a way to obtain a contribution mainly from the topological edge magnons in the spin pumping case.