Magneto-optical recording media with new protective films

Several ceramic films such as AlN, BN, SiN, SiO, SiO2, TiN, and newly developed AlSiN and AlSiON were studied with respect to protection against corrosion of the rare earth-transition metal film and the enhancement of the magneto-optical (MO) effect. The protective and optical properties were investigated as functions of sputtering parameters. The AlSiN and AlSiON films were found to be superior in these properties. For the TbFe films coated with one of these films on polycarbonate substrates, no appreciable change was observed in the MO properties for over 1200 h of aging at 80°C. X-ray diffraction and X-ray photoelectron spectroscopy analyses indicate that the AlSiN and AlSiON films should not be mere mixture of SiN, AlN, etc., but have characteristic binding structure. Their high ability of protection may result from this structure. Refractive index (n) depended on sputtering conditions, and it was high when prepared at low pressure and at high rf power. The AlSiN and AlSiON films exhibited high transparency and high n, and provided sufficient Kerr effect enhancement to the media.