Amorphous CoSm thin films: A new material for high density longitudinal recording

Amorphous thin films of Sm100-xCox(75 < x < 90) were prepared by vacuum deposition in a magnetic field. The preparation conditions and magnetic properties are described. The films exhibit a pronounced uniaxial anisotropy in the film plane with a rectangular shaped hysteresis loop. The magnetization and coercivity are mainly determined by composition. With increasing Sm content the coercivity increases from 30 to 100 kA/m. The magnetization reversal is studied by the angular dependence of the hysteresis properties and by domain observations indicating a nonuniform reversal process. The recording performance measured on 5-in disks shows an improvement in recording density and signal-to-noise ratio compared to traditional longitudinal recording media.