⁵⁷Fe Mössbauer study of the interstitial nitrogen atom effects of NdFe_10.5V_1.5N_x

Magnetic and ⁵⁷Fe Mössbauer spectra measurements were carried out to study the interstitial nitrogen atom effects in the NdFe _10.5V_1.5N_x (0≤x≤2.1) compounds. It is found that saturation magnetization, magnetocrystalline anisotropy, hyperfine fields, and isomer shifts of NdFe_10.5V_1.5N_x are strongly enhanced upon nitrogenation, due to magneto-volume effects and chemical bonding effects of nitrogen atoms. On the basis of the variation of isomer shifts and hyperfine fields as a function of nitrogen concentration, and by using a set of phenomenological formulas, the contributions of magneto-volume effect and the chemical bonding effect to the hyperfine parameters are successfully separated. The pure magneto-volume effect and the chemical bonding effect of the nitrogen atoms will give a positive contribution to the average hyperfine fields and isomer shifts of the Fe atoms in the NdFe _10.5V_1.5N_x nitrides.