The importance of domain nucleation and growth during thermomagnetic recordings in GdTbFeCo disks

A very strong influence of writing laser power on the onset bias field has been observed in a high-Gd-content disk of composition (Gd₈₅Tb₁₅)₂₅(FeCo)₇₅. This observation and the corresponding micrograph 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 shape and size, giving rise to a large readback noise. The irregularities of the written domains are a result of their irregular growth after nucleation. The observed nonuniform nucleation and growth of domains appears to be inevitable in these temperature-compensated writing materials in which the writing temperature is kept from increasing with the Curie temperature. Consequently, it is highly unlikely that the readback signal-to-noise ratio will be improved by utilizing a temperature-compensated writing medium. In fact, it is found that the increase in the writing noise is so high that the signal-to-noise ratio is substantially degraded