Emergence of net magnetization by magnetic field biased diffusion in antiferromagnetic L10 NiMn

Abstract

NiMn is a collinear antiferromagnet with high magnetocrystalline anisotropy (K = -9.7 x 105 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 subsurface region. This leads to an additional ferromagnetic response appearing in the magnetization measurements, which can be removed by surface polishing.