Plasma-enhanced vacuum evaporation of perpendicular Co-Cr magnetic thin films

A novel plasma-enhanced vacuum evaporation process is described for the fabrication of perpendicular Co-Cr thin films for high-density magnetic tape recording. The plasma is excited by an RF coil placed between the source and substrate and is supported by the metal evaporant itself without the need for a carrier gas. The primary effect of the plasma is to increase the perpendicular coercivity, thus allowing a reduction in substrate temperature for better compatibility with low-temperature (and cheaper) polymer supports. It is found that Cr concentration, substrate temperature, and substrate surface preparation are critical to the development and control of perpendicular magnetic characteristics. Transmission electron microscopy (TEM) cross-section analysis reveals a slight increase in grain diameter from film bottom to top, even for films with well-oriented initial layers. A survival-of-the-tallest grain growth model in the high-mobility limit is proposed to explain some of the observed features