MOSSBAUER STUDY ON THE MAGNETIC STATE OF IRON PARTICLES IN FE-N AND FE-ZR-N SOFT-MAGNETIC THIN-FILMS

The magnetic state of alpha-Fe particles and the behaviour of nitrogen and zirconium during annealing in Fe96N4 and Fe85.6Zr7.6N6.8 magnetic thin films have been studied by conversion electron Mossbauer spectro scopy for Fe-57. The crystalline phases present in the Fe-N annealed f ilms were alpha-Fe and gamma'-Fe4N, and those in the Fe-Zr-N annealed films were alpha-Fe and ZrN. In the Fe-N films annealed below 300 degr ees C, about 60% nitrogen is incorporated interstitially into alpha-Fe and the rest is used for the formation of gamma'-Fe4N. In the Fe-N fi lm annealed at 500 degrees C, almost all nitrogen participates in the formation of gamma-Fe4N, leading to the grain growth of alpha-Fe parti cles and an increase in coercive force. The values (291-325 kOe) of in ternal magnetic field of iron sites in alpha-Fe in the Fe-Zr-N films a re much smaller than that (333 kOe) of the iron site in pure alpha-Fe. Even if the Fe-Zr-N films were annealed at 500-700 degrees C, some zi rconium and nitrogen is still incorporated substitutionally and inters titially into alpha-Fe, respectively. In particular, the substitutiona l zirconium depresses the grain growth of alpha-Fe particles, perhaps due to a chemical interaction between zirconium and iron.