Thermal stability and hardness of metastable Co–C composite alloy films

Co–C alloy films containing metastable cobalt carbides have been prepared by a new type of co-sputtering deposition technique and their thermal stability was examined and discussed in terms of the concept of the formation enthalpy. Dynamic hardness and magnetic properties, such as saturation magnetization, were also evaluated for the Co–C alloy films. Both hardness and magnetization of the films were found to decrease almost linearly with increasing fraction of carbon content in the film, suggesting that the measurement of hardness can serve as a monitor of film qualities. It is also shown that the hardness of metastable cobalt carbides is greater than that of the Co–C alloy film.