Origin of uniaxial magnetic anisotropy in MnAlCx: A first-principles study

Abstract

Exploring the thermodynamically metastable L10-ordered τ-MnAl alloy and its intrinsic magnetic properties are of great importance for its potential candidature as rare-earth-free permanent magnets (PMs). Here, based on first-principles calculations, we present a comprehensive investigation of the intrinsic magnetic properties of MnAlCx. The interstitial C-doping is demonstrated to have a substantial influence on the uniaxial magnetic anisotropy energy K u, making MnAlCx appealing for PM applications. We predict a substantial enhancement in K u of up to 2.30 MJ/m3 for x = 1, which is roughly 35% larger than that of pristine MnAl. The atomic resolved and orbital resolved K u, as well as the perturbation theory energy analysis, may be used to understand the cause of this enhancement. Using second-order perturbation theory and electronic structure analysis, we show that increased K u is caused by a complex interplay between tetragonal and orbital distortion due to the C-doping. These findings can aid in the efficient and inexpensive design of PM materials.