A Purely Magnetic Route to High-Harmonic Spin Pumping

TL;DR

This paper introduces a novel, SOC-independent mechanism for high-harmonic spin pumping using purely magnetic structures with an additional static magnetic order, enabling nonlinear spin currents.

Contribution

It demonstrates that purely magnetic systems can generate high-harmonic spin currents without spin-orbit coupling by introducing a secondary magnetic order parameter.

Findings

High-harmonic spin currents can be sustained without SOC.

Magnetic order reshapes the dynamical response to produce higher harmonics.

The mechanism enables ultrafast, nonlinear spin pumping based solely on magnetic structure.

Abstract

Spin pumping provides a fundamental route for dynamical spin transport, yet in its conventional form it produces only linear spin responses at the driving frequency. Recent studies have shown that spin-orbit coupling (SOC) can lift these restrictions and enable strongly nonlinear spin and charge currents. Here we propose a distinct mechanism for high-harmonic spin pumping that operates independently of spin-orbit interactions. We demonstrate that purely magnetic structures can sustain high-harmonic spin currents when an additional static magnetic order parameter is introduced perpendicular to the cone axis of a precessing magnetization. This secondary magnetic order qualitatively reshapes the dynamical response, giving rise to a cascade of higher harmonics in the pumped spin current in the absence of SOC. Our results establish a SOC-independent route to ultrafast and nonlinear spin pumping rooted solely in magnetic structure and dynamics.