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

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 Ku, making MnAlCx appealing for PM applications. We predict a substantial enhancement in Ku 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 Ku, 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 Ku 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.