FE-57 MOSSBAUER STUDY OF FENX(X=0.25-0.91) ALLOYS

Fe-57 Mossbauer measurements have been performed at the first time on iron nitrides, FeNx(x > 0.5), films prepared by rf sputtering and the measurements for gamma-FeN0.09, gamma'-Fe4N, epsilon-Fe2-3N and zeta-Fe2N have been also performed. Two new phases for x > 0.5 have been identified: One has a ZnS-type structure denoted by gamma" Another phase is denoted by gamma"' in which iron atoms constitute a fcc lattice but the details of occupation sites of nitrogen atoms are not yet clear. The isomer shift of gamma" relative to alpha-Fe at 300 K is rather small in comparison with that of other well known nitrides. The room temperature Mossbauer spectra of gamma"' consist of a sum of two doublets. Mossbauer spectra of gamma" at 10 K do not indicate magnetically split pattern, but those of gamma"' show magnetically split patterns at 10 K with the hyperfine fields of 30 T and 48 T, respectively. The component of 48 T is due to oxides, not due to nitrides.