Electron-magnon spin conversion and magnonic spin pumping in antiferromagnet/heavy metal heterostructure

TL;DR

This paper investigates how electron and magnon spins interact at antiferromagnet/heavy metal interfaces, revealing mechanisms for spin conversion and pumping that can be manipulated by magnetic fields, with implications for spintronic devices.

Contribution

It introduces a theoretical model for nonlinear spin conversion and pumping at AFM/heavy metal interfaces, highlighting the role of spin torque and magnetic field control.

Findings

Thermal magnons enable spin transfer between electrons and magnons.

Nonlinear spin pumping occurs at strong spin transfer torque.

Magnetic fields can control thermal spin pumping in AFM heterostructures.

Abstract

We study the exchange between electron and magnon spins at the interface of an antiferromagnet and a heavy metal at finite temperatures. The underlying physical mechanism is based on spin torque associated with the creation/annihilation of thermal magnons with right-hand and left-hand polarization. The creation/annihilation process depends strongly on the relative orientation between the polarization of the electron and the magnon spins. For a sufficiently strong spin transfer torque (STT), the conversion process becomes nonlinear, generating a nonzero net spin pumping current in the AFM that can detected in the neighboring metal layer. Applying an external magnetic field renders possible the manipulation of the STT driving thermal spin pumping. Our theoretical results are experimentally feasible and are of a direct relevance to antiferromagnet-based spintronic devices.