Study on recorded domain characteristics of magneto-optical TbFeCo disks

Domain characteristics (size and shape) of TbFeCo disks of several compositions are studied systematically through direct optical observation under various recording conditions. The relationships among recorded domains, magnetic properties, and recording conditions are also investigated. Magnetic films suitable for very high-density recording are found to have a compensation temperature between room temperature and 100 0C and a Curie temperature near 200 0C. In those films, the formation of domains is stable against fluctuations in laser power and external field. These results can be explained by a simple domain formation model in which coercive force, demagnetizing field, and wall energy at the domain wall are taken into account. Teardroplike domains are observed in the case of relatively long laser pulse recording. Such domains cause detection errors during the domain edge detection. It is also found that recording noise is high under certain recording conditions. The origin of this noise is supposed to be caused by inversely magnetized regions existing in a domain and irregularities in the outline of domains