Co-Cr films with perpendicular magnetic anisotropy

The magnetic properties of RF sputtered Co-Cr films have been studied over a range of preparation conditions extending previous work. Reproducible well-developed perpendicular anisotropy, as would be required for perpendicular recording, was found when the deposition conditions were maintained at an optimum of 170°C substrate temperature, 1.5 KV RF voltage and 5 microns argon pressure. Film thickness was nominally 1 micron. The optimum deposition rate in our system was 120 angstroms/minute due to the differential sputtering rates of Co and Cr. The resulting films had coercivities up to 1500 oersteds and (00.2) hcp X-ray peak width ΔΘ50of 5 degrees, with secondary X-ray peaks observed as well. Columnar growth was observed with grains less than 800 angstrom diameter. A sublayer of poor orientation was observed. Magnetic moment was observed to be about 35% higher than that reported by Iwasaki. Initial background pressure less than 6 × 10^-7torr was essential for formation of well-oriented films. The presence of nitrogen caused the appearance of the fcc phase and the loss of perpendicular coercivity. Loss of coercivity also occurred when film composition was nonuniform.