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. (C) 2000 American Institute of Physics. [S0021-8979(00)69708-6].