Tuning magnetocrystalline anisotropy of α″-Fe16N2 by interstitial impurity doping: A first principles study

The electronic structure and the magnetocrystalline anisotropy of impurity (Li, Be, B, C, and N) doped α″-Fe16N2 were studied by using full potential linearized augmented plane wave method (FLAPW). From the formation energy calculations, it was evident that the 2s and 2p elements except Li could be easily doped into pure α″-Fe16N2. The impurity doping induced local lattice distortions near the impurity site and the magnetic moment near the impurity atom was substantially suppressed. However, the volume of the cell and the total magnetic moment of the doped systems were weakly suppressed compared to the pure α″-Fe16N2. Despite this relatively weak suppression in magnetization, the local distortion contributed to enhancing the magnetocrystalline anisotropy. Due to this enhancement in the anisotropy, the coercive field was also enhanced about 12-16% compared with that in pure structure. Along with the enlarged coercive field, the energy product was also increased. These results may suggest that impurity doped α″-Fe16N2 can be used as potential rare earth free permanent magnet.