THERMAL-CONVERSION OF AN IRON NITRIDE SILICON-NITRIDE PRECURSOR INTO A FERROMAGNETIC NANOCOMPOSITE

Iron nitride films, FeN, in a pure form and in the form of a nanocompo site in silicon nitride were prepared by reactive sputtering using iro n or iron disilicide, respectively, as targets in a nitrogen plasma. I ron nitride decomposes into the elements by heating in vacuum to 800 d egrees C. Intermediate phases such as Fe2N or Fe4N form at lower tempe ratures. The nanocomposites contain the iron phases as particles with an average size of similar to 5 nm dispersed in the amorphous silicon nitride matrix. The magnetic properties of the nanocomposites were est ablished. The precursor FeN-Si3N4 film is paramagnetic, while the Fe-S i3N4, obtained by heating in vacuum, is ferromagnetic and shows typica l superparamagnetic behavior. These films are of interest as recording media with superior chemical and mechanical stability and may be enco ded by localized heating. [S0021-8979(98)02902-8].