First-Principles Prediction of Enhanced Magnetic Anisotropy of alph a"-Phase Fe16N2 With B and C Impurities

Abstract

Intrinsic magnetic properties and uniaxial magnetic anisotropy (Ku) of -phase ordered Fe16N2?xBx and Fe16N2?xCx alloys have been investigated through first-principles calculations. Being in agreement with experimental results, the lattice parameters, magnetic moments, and Ku of -Fe16N2 have been determined. Small addition of B or C dopant atoms enhances tetragonal distortion and Ku up to 0.75 MJ·m?3 for both Fe16N1.75B0.25 and Fe16N1.75C0.25 compounds, which is more than 20% larger compared with that (0.6 MJ·m?3) of -Fe16N2. Furthermore, the presence of B and C reduces magnetic moments of its neighboring Fe atoms at the 4e and 8h sites, resulting in reduced magnetization, due to less electron transfer from Fe to B and C than N. The underlying mechanism for the enhancement in Ku is discussed in connection with the Jahn?Teller lattice distortion, atom-decomposed magnetocrystalline anisotropy, and orbital magnetism.