Experiments towards realization of a recording medium capable of supporting near theoretical density

A novel technique is reported for the preparation of dispersions of cobalt particles with a narrow distribution of diameters around an estimated mean of 8.5 nm. Particles of this size have blocking temperatures close to 220 d egrees C and, dispersed to reduce mutual interaction, they constitute a nea r ideal ultrahigh density recording medium. Production of this medium requi res a two-stage process: reactive sputtering to develop a precursor film of cobalt nitride followed by rapid thermal processing in vacuum. The precurs or film disassociates leaving the required dispersion of cobalt particles. Varying thickness and density in the precursor films and the conditions att ending the disassociation provides some control of the medium magnetic prop erties. Samples with saturation magnetisation (M-s) between 60% and 20% of bulk cobalt exhibit isotropic magnetic properties in-plane with high remane nce and coercivities approaching 2 kOe. (C) 1999 American Institute of Phys ics. [S0021-8979(99)66608-7].