Crystal structure and magnetic properties of “α′′-Fe16N2” containing residual α-Fe prepared by low-temperature ammonia nitridation

Slight enhancement of saturation magnetization to 219 A m2 kg−1 was observed from 199 A m2 kg−1 for the original α-Fe on the intermediate nitrided mixture of “α′′-Fe16N2” with residual α-Fe among the low temperature ammonia nitridation products under 5 T magnetic field at room temperature. The value changed not linearly against the yield as had been expected. Crystal structure refinement indicated that the phase similar to α′′-Fe16N2 had deviations on its lattice constants and positional parameters, compared to previously reported values for α′′-Fe16N2. Spin-polarized total energy calculations were performed using the projector-augmented wave method as implemented in the Vienna ab-initio simulation package (VASP) to calculate magnetic moment on the refined crystal structure of the intermediate “α′′-Fe16N2”. The calculations supported the observed magnetization enhancement in the intermediate nitridation product.