A comparative study of the structural and magnetic properties of gamma-Fe1-xNix alloys and their nitrides gamma '-(Fe1-xNix)(4)N

X-ray diffraction and Mossbauer spectroscopy are performed to investigate g amma-Fe1-xNix alloys and their nitrides gamma'-(Fe1-xNix)(4)N with correspo nding composition, X-ray diffraction shows that both alloys and nitrides ha ve face-centered cubic crystal structure with approximately 18 to 20% expan sion in volume of the nitrides, Mossbauer spectra at room temperature show drastic changes before and after nitrogenation. The changes are also rather different for the samples with lower nickel concentrations and those with the higher ones. For x = 0.25 and 0.30, the alloys mainly exhibit paramagne tic singlets while the nitrides exhibit complex ferromagnetic sextets, For x = 0.75 and 0.78, however, the alloys show ferromagnetic sextets while the nitrides show paramagnetic doublets. The reason for this is carefully disc ussed in terms of the lattice parameter dependence of Curie temperatures, w hich is caused by the introduction of interstitial nitrogen atoms into the Fe-Ni alloy structure.