Advanced MO materials and storage devices toward 100 Gb/in/sup 2/

Magneto-optical (MO) disks possess the advantage of high-density recording compared with nonmagnetic optical disks, because MO recording is similar to the perpendicular magnetic recording of hard disk. The high density storage requires very tiny domain recording and the MO signal then decreases rapidly with decreasing domain area. The key to achieving high-density recording is enhancement of the small MO signal using techniques like such as giant magneto resistance (GMR). As a solution, the magnetic domain expansion readout method has already been proposed.