Fe2P based alloys as possible rare-earth free permanent magnets

The Fe2P alloy exhibits high saturation magnetization, large uniaxial magnetic anisotropy, and excellent thermal stability, which make it a potential permanent magnet; however, it suffers from relatively low coercivity Hc, and Curie temperature T below room temperature. Herein, using systematic theoretical and experimental investigations, it is demonstrated that multi-element substitutions of Co for Fe, and Si and B for P site (among 3d and 2p-3p substitutional elements) enhance permanent magnetic performance, while retaining its thermodynamic stability. Specifically, we find Hc values up to 1 kOe at room temperature and T values more than 500 K at a magnetic field of 2 T in (Fe,Co)2(P,Si,B), leading to the theoretical energy product (BH)max of 126 kJ/m3 and hardness parameter no less than 1 at room temperature, which are notably larger than the corresponding values for Fe2P and (Fe,Co)2(P,Si) alloys. These results suggest a venue for significant advances in the development of permanent magnetic materials based on the Fe2P-type structure.