Effects of target structure on the properties of MO recoding media produced in a large-scale vertical in-line sputtering system

The metallurgical states of rare-earth-transition-metal targets were found to have a significant effect on the performance of magnetooptical (MO) recording thin films. Polar Kerr MO hysteresis loops of the films were measured as a function of temperature at a HeNe laser wavelength. B-H hysteresis loops were measured by a vibrating sample magnetometer at the room temperature. The study indicates that in a vertical in-line sputtering system, a rectangular alloy target containing about 25% of the intermetallic phase produces a negligibly small composition gradient in DC-magnetron-sputtered films. With a proper aperture to mask off oblique incident coating flux, coercivity and thickness variations of less than ±5 and ±2% have been achieved reproducibly on 5.25-in disks