Seiji Okada

A new protective film for magneto‐optical TbFeCo media

A new protective film, Tb‐SiO2, was developed to increase the lifetime of TbFeCo magneto‐optical disks. Since Tb, a rare‐earth metal, is quite easily oxidizable, an efficient protective layer is essential to assure the stability of magneto‐optical disks. Given that vacuum‐deposited SiO2 film acts as an oxidation‐inducing layer, unlike SiO2 on a thermally oxidized silicon wafer, we invented a new protective film, Tb‐SiO2, in which Tb is intended to trap active oxygen in the vacuum‐deposited SiO2. The results were excellent and we estimate the lifetime of TbFeCo disks with Tb‐SiO2 as an underlayer and overlayer, at more than 20 years at 40 °C, 90% relative humidity. The properties and protection effects of Tb‐SiO2 are described.