Domain erasure and formation in direct overwrite magneto-optic recording

Abstract

The erase and write processes in single layer direct-overwrite magneto-optic recording materials were investigated utilizing a stroboscopic microscope system with 10-nsec time resolution. The effects of thermal magnetization reduction are addressed and limited by image subtraction techniques. With this technique the erase process is shown to be a collapse process which occurs during heating, rather than cooling. Galvanometer driven beam scanning is utilized to write and erase ‘‘stripe’’ domains at velocities up to 5 m/s. Scanning write and scanning continuous beam erase are investigated stroboscopically, providing surprising new data on these processes. The erase process for a ‘‘stripe’’ domain is shown to proceed from the end of the domain, and in front of the approaching erase laser beam. Jitter in the leading edge of the written domain is observed, and may be responsible for the noise levels observed in these materials. The data indicate that the erase process is driven by a combination of temperature and temperature gradient. The write behavior can be explained by either a post-laser pulse nucleation or by movement of the trailing domain wall.