Effects of alloying and strain on the magnetic properties of Fe16N2

The electronic structure and magnetic properties of pure and doped Fe16N2 systems have been studied in the local-density (LDA) and quasiparticle self-consistent GW approximations. The GW magnetic moment of pure Fe16N2 is somewhat larger compared to LDA but not anomalously large. The effects of doping on magnetic moment and exchange coupling were analyzed using the coherent potential approximation. Our lowest estimate of the Curie temperature in pure Fe16N2 is significantly higher than the measured value, which we mainly attribute to the quality of available samples and the interpretation of experimental results. We found that different Fe sites contribute very differently to the magnetocrystalline anisotropy energy (MAE), which offers a way to increase the MAE by small site-specific doping of Co or Ti for Fe. The MAE also increases under tetragonal strain.