First-Principles Prediction of Enhanced Magnetic Anisotropy of α-Phase Fe16N2 With B and C Impurities

Intrinsic magnetic properties and uniaxial magnetic anisotropy (K-u) of alpha ''-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 K-u of alpha ''-Fe16N2 have been determined. Small addition of B or C dopant atoms enhances tetragonal distortion and K-u 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 alpha ''-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 K-u is discussed in connection with the Jahn Teller lattice distortion, atom-decomposed magnetocrystalline anisotropy, and orbital magnetism.

Automated summary

The intrinsic magnetic properties and uniaxial magnetic anisotropy of alpha ''-phase Fe16N2-xBx and Fe16N2-xCx alloys were investigated through first-principles calculations. The addition of B or C dopant atoms enhances tetragonal distortion, magnetic properties, and the K-u values of the alloys, while simultaneously reducing the magnetic moments of Fe atoms due to less electron transfer compared to N. The enhancement in K-u is attributed to Jahn Teller lattice distortion, atom-decomposed magnetocrystalline anisotropy, and orbital magnetism.