A magneto-optic recording system using TbFeCo

A large capacity magneto-optic recording system has been developed for mass data storage. The recording material is an amorphous magnetic film of TbFeCo, which is magnetizes vertically. The TbFeCo film is deposited onto a plastic substrate by sputtering. It has a Kerr rotation angle of 0.35°, a Curie temperature of 190°C, and an amorphous-crystal transition temperature of 240°C. The 30cm-diameter disk has a double-sided structure and each side consists of a magnetic layer and protective layers. Using mastering and replication techniques, grooves with address headings are produced in the polycarbonate plastic substrate at a track-pitch of 1.6μm. A lightweight, high performance optical pickup is operated at an average seek time of less than 100msec. The raw bit error rate (BER) of the disk is currently of the order of 10^-5and the system is designed to provide the corrected BER of 10^-12using a Cross Interleave Reed-Solomon Code. The system consists of a 1-Gbyte magneto-optical memory disk drive to be used as a code memory for computers, a controller unit capable of being expanded to 4-Gbytes, and an interface module called the Small Computer System Interface (SCSI).