Media for erasable magnetooptic recording

Amorphous rare-earth-transition-metal alloys are considered as materials for magnetooptic information storage. They can be prepared by evaporation or sputtering on glass or polymer substrates. The alloys are ferrimagnets and exhibit a uniaxial magnetic anisotropy. The magnetic and magnetooptic properties can be well tailored by the composition as well as the deposition conditions. The information is stored by memory magnetic domains which can be written by a thermomagnetic switching process. The reading process utilizes the magnetooptic Kerr effect. In both cases the temperature profile of the saturation magnetization, the uniaxial anisotropy, and in particular the coercivity are of primary importance. At present, the most prominent candidates for device applications are GdTb-FeCo and Tb-FeCo alloys. Carrier-to-noise values up to 61 dB (30 kHz) have been achieved using magnetooptic disks