Synthesis and magnetic properties of tetragonally ordered Fe2Ni2N alloy using topotactic nitriding reaction

Tetragonally ordered Fe2Ni2N powder was successfully synthesized from L10-FeNi using a nitrogen topotactic reaction. The magnetic properties and structural stability of the tetragonally ordered Fe2Ni2N were examined using first principles calculations. The nitriding process gives 96 wt% of tetragonally ordered Fe2Ni2N phase and the rest is the more nitrided phase of FeNiN. Analysis of the crystal structure confirmed that the c/a is 0.989 for the tetragonally ordered Fe2Ni2N, which is consistent with the results of the first-principles calculations. Magnetization measurements reveal that the Curie temperature and thermal decomposition temperatures are 441 and 667 K, respectively. The high field magnetization processes at 10 K indicate that the sample contains a component of high magnetic anisotropy energy Ku. The Ku estimated by the law of approach to ferromagnetic saturation is 1.51 MJ/m3, which is in reasonably good agreement with that obtained by the first-principles calculations 1.96 MJ/m3.