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 sputter ing of cobalt metal, cobalt boride, or cobalt silicide as targets, res pectively, in a nitrogen plasma. Cobalt nitride decomposes into the el ements by heating under vacuum at 500 degrees 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 precu rsor cobalt nitride is paramagnetic while the cobalt dispersions, havi ng dimensions smaller than single magnetic domain, show characteristic s typical of those systems such as superparamagnetism and, at temperat ures lower than the blocking temperature, marked hysteresis. The coerc ive 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 .