True Direct Overwrite in Single Layer Magneto-Optic Recording

Single layer direct overwrite materials were investigated with the goal of improving the carrier-to-noise ratio (CNR) of these films. Both experimental and modelling study of the dynamics of direct overwrite without defined bit positions was combined with study of a large matrix of material samples to provide guided material improvements. Experimental study included magnetic measurements, CNR measurements, and observation of magnetization and thermal dynamics with stroboscopic polarized light microscopy. Thermal modelling was used to gain further insight into the thermal dynamics of direct overwrite. The results showed that flat substrates, high disc velocities, and materials which by means of sputter-etching the underlayer exhibit smooth wall motion can combine to produce true multi frequency direct overwrite with CNR’s of 42 dB or better. This is about 15 dB better than previously reported. © 1993 IEEE