Magneto-optical disk

摘要

A magneto-optical disk having a four-layer structure formed of a first protective dielectric layer, a recording magnetic layer, a second protective dielectric layer and a reflective metal layer is disclosed. The constraints for the film thicknesses of the various layers are determined not only from the optical and magneto-optical aspects, but from the aspect of the dynamic thermal response. The recording magnetic layer is a magnetic layer mainly formed of TbFeCo and having a film thickness of not less than 180 ANGSTROM and not more than 280 ANGSTROM . The first protective dielectric layer is a nitride film having a film thickness such that the product of its refractive index and the film thickness is not less than 0.2 and not more than 0.35 times the wavelength of the laser light employed. The second protective dielectric layer is a nitride film having a film thickness such that the product of its refractive index and the film thickness is not less than 0.1 and not more than 0.15 times the wavelength of the laser light employed. The the reflective metal layer is a metal layer having a film thickness of not less than 500 ANGSTROM and not more than 1000 ANGSTROM , with the metal being electro-chemically less noble than the material of the recording magnetic layer and having a reflectivity at the boundary with the second protective dielectric material of not less than 70%.