Thermal stability of Co80Pt20-SiO2 granular films sputtered on DC pulse biased substrates

Granular Co₈₀Pt₂₀-SiO₂ films have been prepared with thicknesses of ~15 nm using a novel pulsed dc bias technique. This enabled the growth of thermally stable films with coercivities as high as 2.3 kOe without annealing. The CoPt granules are randomly oriented with a slight (1010) texture with diameters of 5-10 nm at 51% CoPt volume fraction. Measurement of the time-dependent coercivity was used to extract the value of intrinsic switching field Ho and the thermal stability factor KV/kT by fitting to Sharrock´s formula. The value of H₀ decreases from 3.5 kOe at 41% CoPt to 2.5 kOe at 58% CoPt while KV/kT increases from 78 to a maximum of 236 at 56% CoPt before decreasing to 160 at 58% CoPt. The coercivity was relatively flat from 45% to 58% CoPt, presumably because of the offsetting effects of the increase in H₀ and the decrease in KV/kT over this range