Antiferromagnetic Ordering Enhanced Magnetic Damping in Mn2Au/CoFeB Bilayers

TL;DR

This study investigates how antiferromagnetic Mn2Au influences magnetic damping in Mn2Au/CoFeB bilayers, revealing temperature-dependent exchange coupling and spin transfer mechanisms relevant for spintronic applications.

Contribution

It provides new insights into AFM/FM dynamics by demonstrating enhanced spin transfer and damping modulation due to AFM ordering in Mn2Au/CoFeB bilayers.

Findings

Magnetic damping increases as temperature decreases from 160 K to 10 K.

Exchange coupling field H_rot increases with decreasing temperature.

Enhanced spin angular momentum transfer is mediated by AFM ordering.

Abstract

Antiferromagnets (AFMs) hold significant potential for spintronic devices owing to their insensitivity to external magnetic fields and the absence of stray fields. Beyond these inherent advantages, an AFM can manipulate the magnetic dynamics of a ferromagnet (FM) layer in AFM/FM bilayers, whereas the mechanism of such manipulation remains controversial. Here, we investigate the magnetic dynamics of AFM/FM Mn2Au/CoFeB bilayers via Ferromagnetic Resonance (FMR). It is found that the N\'eel temperature of 2-nm-thick Mn2Au is as low as ~40 K, in sharp contrast to that of bulk Mn2Au, which exceeds 1000 K. In the Mn2Au(2 nm)/CoFeB(4 nm) bilayer, the magnetic damping ${\alpha}$ of the CoFeB layer increases from 0.013 to 0.047 as temperature decreases from 160 K to 10 K, accompanied by a synchronous increase in the exchange coupling field H_rot. Such an increase in ${\alpha}$ is attributed to the enhanced spin angular momentum transfer from CoFeB to Mn2Au, mediated through AFM-FM exchange coupling between Mn2Au and CoFeB, which is enhanced by the Mn2Au antiferromagnetic ordering as the temperature decreases. Our study provides deeper insights into AFM/FM dynamics and spintronic storage technology.