Spatially-resolved magnetic imaging of magneto-optic recording

The spatial evolution and eventual collapse of thermo-magnetically written marks on a conventional TbFeCo magneto-optic medium were imaged as functions of temperature in the presence of an external field. Magnetic force microscopy images with 100 nm scale resolution were obtained from the same area of the medium. The sequential imaging made it possible to observe the domain wall motions of individual marks. Our results indicate that, due to variations in local mechanical and magnetic properties of the medium, wall motion does not proceed uniformly in all directions, but is strongly enhanced in certain areas while impeded in others. These effects lead to formation of complex domain shapes prior to collapse. Quantitative parameters, such as the critical radius for domain collapse as well as domain wall widths, have also been measured.