Study of the Multi-layer Structure for the Magneto-optical Disk

This paper describes the magneto-optical disk with multi-layer structure. The recording medium that is constructed by amorphous rareearth and transition metal alloy, transparent films and a reflective film has been studied for higher signal quality and higher reliability. The design concept of the multi-layer structure is to make the Kerr rotation angle maximum using optical interference in the films and to improve reliability by stable transparent and reflective films. The optical characters are calculated for the design with thicknesses and refractive indexes of the films. The nitride transparent film is selected for reliability after testing some transparent films. The magneto-optical disks were checked after exposed to high temperature and high humidity. The life of the medium itself and the recording bit are estimated from these tests. The high recording desity 108bit/cm2 and more than 10 years life of the media are achieved with the multi-layer structure. The rewritable and removalble memory medium that has large capacity is realized.