INFLUENCE OF LAYER STRUCTURE ON WRITE ERASE REPETITION CHARACTERISTICS OF MAGNETOOPTICAL DISKS

The relationship between erase-write characteristics or write/erase re petition characteristics and the layer structure of magneto-optical di sks, was studied both experimentarily and by computer simulation. For tri-layer structure disks such as Sub./SiN(x)/TbFeCo/SiN(x), an erase power of 11.5 mW is needed to erase a recorded domain, perfectly. The carrier level of tri-layered disks decreases with increasing write/era se repetition cycle. This is due to structure relaxation in the record ing film which is caused by heating above a maximum temperature of 350 -degrees-C. A quadri-layer structure is studied which has a thinner re cording layer and a metal layer, whose thermal conductivity is low. Wi th this structure, the carrier level decreases after repeated write/er ase processes. As the maximum temperature on the recording film is hig her than 370-degrees-C, there is also structure relaxation in the reco rding film. When Al, whose conductivity is large, was used as the meta l layer, the number of the write/erase repetition cycles was increased and there was no structure relaxation when the maximum temperature wa s lower than 300-degrees-C. The disk incorporating this structure has a large carrier to noise ratio. Using these results, the disk structur e was optimized. After repetition of erase and write, C/N did not chan ge. This disk has high reliability against thermal resistance.