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.

Graphical abstractCrystal structural parameters slightly change in the intermediate nitrided “α′′-Fe16N2” from those in α′′-Fe16N2 to show the magnetization maxima in the mixture of “α′′-Fe16N2” and the residual α-F.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Larger magnetization was observed than the value of Fe16N2 on its intermediate nitrided mixture with residual α-Fe. ► The enhancement was related to the crystal structural deviation from Fe16N2 on the intermediate nitride. ► It was supported by spin-polarized total energy calculation using the deviated structure.