First-principles prediction of rare-earth free permanent magnet: FeNi with enhanced magnetic anisotropy and stability through interstitial boron

Ab initio electronic structure calculations reveal that interstitial 2p elements (B, C, and N) have dramatic effects on the structural stability and intrinsic magnetic properties of L10-phase FeNi. Among the 3 possible interstitial impurities, only the B improves the L10-phase stability of FeNi and enhances its uniaxial magnetic anisotropy (0.7 MJ m−3) up to 2.6 MJ m−3. The underlying mechanism is elucidated in terms of single-particle energy spectra analyses along with atom- and orbital-resolved magnetocrystalline anisotropy energy, where both the Fe and Ni 3d level changes induced by charge rearrangement and 2p-3d hybridization are responsible. These findings point toward feasibility of enhancing the structural stability and energy product of 3d-only magnetic metals through the interstitial doping with 2p nonmetal elements.