The Effects of Temperature-Dependent Oxidation and Diffusion on the Magnetic Stability of Amorphous CoSmCu Thin Films
There is great interest in the use of CoSmCu thin films for computer data storage applications due to evidence that their magnetic properties can potentially be favorable for increasing data storage density. However, there is also concern about the magnetic stability of these compounds at elevated temperatures, due to the propensity of lanthanide metals, such as samarium, to oxidation. This study examines the effects of annealing on the magnetic properties of CoSmCu thin films. Specifically, the effects of oxidation and diffusion processes and the relationship of these processes to film composition are examined. The results suggest that samarium oxidation, which increases the magnetization of CoSmCu thin films, occurs at lower annealing temperatures due to oxygen located in the under-layer of the thin film, while oxidation at higher temperatures is due to atmospheric oxygen. The results further suggest that this high-temperature oxidation can be avoided with the use of a layer of tantalum in the thin film. It is also shown that diffusion of chromium or tungsten atoms into magnetic CoSmCu layer tends to decrease the magnetization, and the rate of diffusion is dependent on the material used.