Nanocrystalline garnet disks for magneto-optical recording media

Nanocrystalline garnet films exhibit recording characteristics at short wavelengths as high as those of rare-earth-transition metal films or Pt/Co multilayers. The memory layer of a high-Bi-content garnet with 50 nm grains was obtained by crystallizing the amorphous film on a low-Bi-content garnet underlayer. The lattice mismatch introduced between the two layers is necessary for the formation of nanometer-size grains. The media noise of the bilayer is greatly reduced by applying a non-magnetic garnet as the underlayer. We have prepared the bilayer garnet film on a 130 mm glass disk with a groove, and obtained a carrier-to-noise ratio of 42 dB at a 0.47 mu m mark length at a wavelength of 488 nm. Small marks of 0.38 mu m have been also successfully recorded on the disk.