MAGNETIC DOMAIN FORMATION IN TB23FE77 THIN-FILM ON A MOVING MAGNETOOPTICAL DISK WITH MAGNETIC-FIELD MODULATION RECORDING

In this paper, the magnetic domain formation process on a moving disk for Tb23Fe77 magneto-optical recording thin film under the magnetic fi eld modulation recording was investigated by a new simulation method, The simulation results showed that the convex prior edge of the domain was instantly formed and pinned when the magnetic field changed from low state to high state, Then, the domain boundary was lengthened oppo site to the disk moving direction without changing the width during th e high state of the applied magnetic field, As the magnetic field chan ged from high state to low state, the concave posterior edge of the do main was simultaneously formed and pinned, and the domain became a clo sed chevron shape, Both edges closely resemble the Curie temperature c ontour, There existed a threshold applied magnetic field strength, and the domain could not be formed when the applied field strength was be low the threshold value, The value of the threshold field was approxim ately the same as the demagnetizing field around Tc, but reversed in p olarity, and it increased with the laser power, The domain width incre ased as the applied field increased above the threshold value, and it rapidly became saturated when the applied field was about 30 Oe greate r than the threshold value, There also existed a threshold laser power , below which the domain could not be formed, The threshold power was 3.3 mW for Tb23Fe77. The domain width increased monotonically with the laser power for high applied magnetic field, and it increased (then d ecreased) with the laser power when the applied magnetic field was clo sed to the threshold value.