the importance of domain nucleation and growth during thermomagnetic recording in GdTbFeCo disks

Abstract

A very strong influence of writing laser power on the onset bias field has been observed in a high Gd-containing disk of composition (Gd<inf>85</inf>Tb<inf>15</inf>)<inf>25</inf>(FeCo)<inf>25</inf>. This observation and the corresponding micrographs of written domain patterns suggest that domain nucleation is responsible for such unusual behavior. Furthermore. the domains written on this disk are very irregular in both share and size, giving rise to a large readback noise. The irregularities of written domains is a result of irregular growth of domains after they nucleate. The observed nonuniform nucleation and growth of domains seems inevitable in compensation temperature writing materials. Consequently, it is highly unlikely to have the readback signal-to-noise ratio improved by utilizing a compensation temperature writing medium. In fact, the increase in the writing noise is so high that the signal-to-noise ratio is substantially degraded. © 1989 IEEE