# Emergence of net magnetization by magnetic-field-biased diffusion in antiferromagnetic L1$_0$ NiMn

## TL;DR

This study demonstrates that magnetic-field-biased diffusion during annealing induces net magnetization in antiferromagnetic NiMn, supported by experimental and ab initio modeling, revealing surface oxidation effects and magnetic moment pinning.

## Contribution

It introduces a novel mechanism of magnetic-field-biased diffusion causing net magnetization in NiMn, supported by experimental data and ab initio calculations.

## Key findings

- Magnetic annealing induces strongly pinned magnetic moments.
- Surface oxidation causes Ni enrichment and ferromagnetic response.
- Magnetization can be controlled by surface polishing.

## Abstract

NiMn is a collinear antiferromagnet with high magneto crystalline anisotropy ($K_2=-9.7\times10^5\;\text{J m}^{-3}$). Through magnetic annealing of NiMn with excess Ni, strongly pinned magnetic moments emerge due to an imbalance in the distribution of Ni in the antiferromagnetic Mn-sublattices. The results are explained with a model of magnetic-field-biased diffusion, supported by ab initio calculations. Another observation is the oxidation of Mn at the surface, causing an enrichment of Ni in the sub-surface region. This leads to an additional ferromagnetic response appearing in the magnetization measurements, which can be removed by surface polishing.