Optimized structure of sputtered garnet disks

The optimum structure of the sputtered garnet magnetooptical disk was investigated by numerical calculations and experiments. From the Faraday rotation, Faraday ellipticity, refractive index, and extinction coefficient, the authors determined the dielectric tensor elements of a sputtered garnet film. Using these values, they calculated the thickness dependence of the magnetooptical rotation angle, the reflectivity, and the reproduced signal amplitude of the disk with a reflecting layer. These results were then compared with measurements. The optimum garnet thickness and reflector material for a sputtered garnet disk were found. The optimum structure has a carrier/noise ratio of 60 dB at a carrier frequency of 0.6 MHz and possesses good recording sensitivity