Tracing magnetic atom diffusion with annealing at the interface between CoMn alloy and MnGa layer by X-ray magnetic circular dichroism

TL;DR

This study investigates how annealing affects magnetic atom diffusion and interfacial magnetic coupling between CoMn alloy and MnGa layers using XMCD, revealing changes in magnetic properties and interfacial reactions.

Contribution

It provides new insights into the interfacial magnetic coupling modulation and atomic diffusion mechanisms in CoMn/MnGa heterostructures through element-specific analysis.

Findings

Annealing switches magnetic coupling from parallel to antiferromagnetic.

Interfacial reactions promote formation of Mn and Co2MnGa layers.

Diffusion of Mn atoms reverses the perpendicular magnetization direction.

Abstract

The magnetic atom diffusion at the interface between CoMn alloy and MnGa layer with annealing is studied using x-ray magnetic circular dichroism (XMCD) analysis. We found that the spins in bcc CoMn are coupled parallel to those in perpendicularly magnetized MnGa layer under the as-grown conditions, while the post-annealing modulates the interfacial magnetic coupling to antiferromagnetic in Co. The element-specific hysteresis curves at each absorption edge revealed the large coercive fields in Mn and Co through the exchange coupling with MnGa. After the annealing process, the changes of XMCD spectral line shapes are related to the interfacial reactions promoting the formation of Mn and Co2MnGa layers, which is deduced from the analysis of transmission electron microscopy. The interfacial diffusion of Mn atoms modulates the magnetic exchange coupling between Mn and Co sites and reverses the direction of perpendicular magnetization.