High resolution measurement of coercivity variations in magneto-optical recording media

The coercivity of amorphous rare-earth-transition-metal magnetooptical recording media has been measured as a function of position on the films utilizing a micro-Kerr-hysteresis-loop tracer with an effective measuring aperture of 0.5 μm. The local variations of wall motion coercivity (H_c) in films whose magnetization reversal was dominated by nucleation were as large as 20%. In contrast, H_c in films whose magnetization reversal was dominated by domain-wall motion exhibited a negligibly small variation from place to place. It was found that the fields required to collapse micron-sized domains were typically 20% less than H_c as measured above. The predominant magnetization-reversal mechanism in the films is mainly determined by fabrication processes