Abstract

The 130-mm magneto-optical disk has already been marketed, and experimental 90-mm drives have been fabricated to develop compact, extremely efficient low-cost models. Such disks are now being used by individual customers and, in such cases, must be available at a low price. Magneto-optical disks mainly use TbFeCo for their recording material. The magneto-optical disk we developed uses DyFeCo film, which is about two-thirds less expensive than TbFeCo because dysprosium is less expensive than terbium. It had been thought that DyFeCo had a lower Curie temperature and smaller perpendicular magnetic anisotropy than TbFeCo, leading to questions about signal quality and recording bit stability. Unfortunately, no reports on the practicality of DyFeCo have been published thus far. The practical disk we developed has an optimized DyFeCo composition and configuration. For the protective film, we originally developed a very efficient Tb-SiO₂ film [1], but replaced it with cerium, which is less expensive. The Ce-SiO₂ film was as protective as the Tb-SiO₂ film, which we have already reported.

© 1991 Optical Society of America