Magnetooptical recording technology toward 100 Gb/in2

Concerning areal recording density, magnetooptical (MO) disk possesses an advantage compared to another optical disks and also magnetic hard disk (HDD), since the linear density of MO disk can be increased by using a perpendicular magnetic recording, and the track density also can be increased by using an optical tracking method. On the other hand, in the region of high density HDD, demagnetization problem is discussed for archival data storage. However, since the coercive force of MO recording material is over five times larger than that of HDD, it does not become such a severe problem for MO recording. In case of very-high-density recording, the readout signal is drastically reduced due to decreasing both the recorded domain size and the optical resolution. However, in the case of MO, the small readout signal can be enhanced by using a novel readout technique named as magnetic amplifying MO system and the extremely small signal also can be detected. Thus, it is found that the MO has probability of achieving an extremely high density storage such as 100 Gb/in²