Noise Characteristics of Amorphous Rare Earth-Transition Metal Thin Films

The origin of media noise affecting the polarization of the incident beam (and with intensity proportional to the reproduced signal) in magneto-optical reproduction was studied. RE-TM films were RF sputtered on glass disks, and the C/N ratio measured. The C/N was low at peripheral disk regions, probably due to the sputtering geometry, which would also cause the magnetization to be diagonal rather than perpendicular. Magnetic field annealing resulted in lower noise levels, also consistent with the theory that deviation of the magnetization from the perpendicular may affect the medium noise.