Effects of Pt and Ta addition on compositional microstructure of CoCr-alloy thin film media

Compositional segregation structures of Co–Cr–Ta, Co–Cr–Pt, and Co–Cr–Pt–Ta thin film media with Cr concentrations of about 15 at. % were studied using an analytical transmission electron microscope. Cr atoms in the CoCrTa specimen are extremely localized around the grain boundaries with a maximum concentration of about 23 at. % with a width of 1 nm, while that inside the grain is about a half of the average composition. The Co–Cr–Pt specimen shows Cr segregation at grain boundaries with a maximum concentration by 4 at. % greater than the average composition. The Cr concentration inside the grain is kept nearly same with the average concentration. The Co–Cr–Pt–Ta specimen shows a degree of Cr segregation between the Co–Cr–Ta and the Co–Cr–Pt systems. The Cr enrichment at bicrystal grain boundaries is broader and weaker than those at the normal grain boundaries.