Direct overwriting capability of magneto-optical disks

Erasing magneto-optical disks were studied using constant frequency pulses. The magnetic layer was Gd12Tb12Fe76. The linear velocity was 7.2 m/s and writing and rewriting were done at 1.8 MHz. The magnetic field was the same during writing and erasing. If the erasing power is too low, bits are incompletely erased, and if the erasing power is too high, erase pulses nucleate domains. Erasing performance can be improved by high frequencies and low duty cycles. Erasing performance decreases as the magnetic field in write direction becomes stronger. However, almost the same rewriting C/N as the original C/N can be obtained in a weak magnetic field. We obtained a rewriting C/N of 29 dB, while an original C/N was 31 dB at a magnetic field of +50 Oe.