Compositional inhomogeneities in Co-Cr-Ta/Cr films for longitudinal magnetic recording

The change in compositional distribution of sputtered Co-12at.%Cr-2at.%Ta films deposited on Cr underlayers was investigated as a function of substrate temperature, using spin-echo ⁵⁹Co nuclear magnetic resonance. It was observed that a highly Co-rich component with an estimated Co content of about 97 at.% precipitates as the substrate temperature increases from 25 to 250°C. The compositional microstructure observation suggests compositional separation within grains having Cr-enriched grain boundaries. The precipitation is in accordance with an increase in coercivity and a decrease in coercive squareness and media noise. The compositional inhomogeneities observed in Co-Cr-based alloy films for either longitudinal or perpendicular recording media are thought to be effective in promoting the change from a continuous structure to a particulate structure suitable for high-density magnetic recording