Temperature-Dependent Magnetic Properties of Bi-Doped Fe16N2: First Principles and Atomistic Study

Using the first principle calculations, we investigated the temperature-dependent magnetic properties of Bi-doped Fe16N2. We found that the Bi doping resulted in the lattice expansion and consequently the volume expansion occurred. Due to this volume expansion, the saturation magnetization of Bi-doped system was suppressed by 12% compared with that of pure Fe16N2. Nonetheless, the hybridization effect between Fe 3d and Bi 6p orbitals contributed to enhancing the magnetocrystalline anisotropy from 0.73 meV/cell in pure Fe16N2 to 1.57 meV/cell in Bi-doped system. Through the temperature-dependent magnetization dynamics, we found that the Bi-doped system had a coercive field of 9.63 kOe at 300 K while the pure Fe16N2 alloy had a coercive field of 3.61 kOe. Furthermore, a maximum energy product of 70.2 MGOe at 300 K was found in Bi-doped system. Overall, we propose that the Bi-doped system can be a potential rare-earth-free permanent magnet (PM).