Large magnetic anisotropy in Co-Fe-Ni-N ordered structures: a first-principles study.

Material design of promising rare-earth free permanent magnet requires tailoring and controlling the intrinsic magnetic properties namely large saturation magnetization μ 0 M s , giant uniaxial magnetic anisotropy K u , and high Curie temperature T C . Based on first-principles electronic structure calculations, we present a detailed analysis for the intrinsic magnetic properties of Co x Fe 1- x Ni and Co x Fe 1- x NiN 0.25 ordered structures. We predict an enhanced structural stability with improved K u ranging from 1.53-2.29 MJ m -3 for Co x Fe 1- x NiN 0.25 ordered structures, with the exception of CoNiN 0.25 having planar anisotropy. Detailed analysis of the predicted large K u , based on perturbation theory and electronic structure calculations, is attributed to the cumulative effect of contribution from the increased tetragonal distortion and induced orbital distortion from the simultaneous Co substitution and interstitial N-doping. By tailoring the K u , we may create efficient and affordable PMs, bridging the gap between commonly used ferrite and high-performance Nd-Fe-B magnets.