Electrochemical studies on CoCr films as a function of substrate temperature and post-deposition heat treatment

The corrosion resistance of dc magnetron sputtered Co79Cr21 thin films is studied by electrochemical means as a function of substrate temperature Ts ranging from −196 to 375 °C. The corrosion activity increases with Ts and peaks at ∼300 °C. This behavior correlates with the substrate temperature dependence of saturation magnetization of the films. The source of corrosion is suggested to be primarily associated with the segregated Co‐rich material. Heat treatment in vacuum at 500 °C significantly improves the corrosion resistance. Evidence is provided suggesting dilution of Co concentration in segregated Co‐rich regions is responsible for this improvement.