First-principles prediction of magnetic properties in Fe(Co,Ni)(C,N)0.5 alloys

To explore a candidate for rare-earth-free magnets, the effects of the light elements (C,N) addition on the magnetic properties in FeCo and FeNi ordered alloys were examined using first-principles calculations. Among Fe(Co,Ni)(C,N)0.5 alloys, we found that FeNiC0.5 is the most promising, because its uniaxial magnetic anisotropy constant Ku is expected to be 3.0 MJ/m3 (five times Ku of L10-type FeNi) and the increase in the Curie temperature TC by the addition of C was observed. The mechanism for the enhancement of Ku and TC can be understood by the basic concepts of the physics of magnetism. Despite being nonmagnetic themselves, light elements have the potential to improve the fundamental properties of magnetic materials.