Ferromagnetic nanocomposite films of cobalt in a ceramic matrix formed by thermal decomposition of cobalt nitride, CoN, precursor

Cobalt nitride films, CoN, in a pure form and also as a nanocomposite in boron nitride or silicon nitride were generated by reactive sputtering of cobalt metal, cobalt boride, or cobalt silicide as targets, respectively, in a nitrogen plasma. Cobalt nitride decomposes into the elements by heating under vacuum at 500°C. The nanostructure of the composites was preserved in the heating treatment thus creating a fine dispersion (<10 nm) of cobalt particles, in a ceramic matrix. The magnetic properties of the nanocomposites were established. The precursor cobalt nitride is paramagnetic while the cobalt dispersions, having dimensions smaller than single magnetic domain, show characteristics typical of those systems such as superparamagnetism and, at temperatures lower than the blocking temperature, marked hysteresis. The coercive fields at 5 K for the BN and Si₃N₄ nanocomposites are 3250 and 850 Oe, respectively. These films are of interest as data recording media.