Investigations of compositional separation in Co-Cr thin film recording media

We investigated the effect of a Ge underlayer and substrate temperature during film deposition (T_s) on the compositional distribution in Co₇₉Cr₂₁ films using spin echo nuclear magnetic resonance and preferential chemical etching. For films deposited at elevated T_s we observed drastic compositional separation (CS) leading to a Co enriched phase with approximately 5 at% Cr on both Ge and polyester. Chemical etching revealed chrysanthemum pattern (CP) type microstructures. For lower T_s films we observed less marked CS with a distinct etched microstructure in the film deposited on Ge and no clear etched microstructure in the film deposited on polyester. Results from NMR and chemical etching studies agreed very well with those from X-ray microanalysis.