Reliability of Magneto-Optical Memory Disks

TbFeCo recording layers were deposited onto polycarbonate (PC) and PMMA substrate disks and their characteristics were examined and compared. The more durable PC substrate disks had lower C/N ratios than the PMMA disks. The use of SiO
₂
protective layers improved the bit-error rate (BER) of the PC substrates from 2 × 10
^-3
to 7 × 10
^-5
, and there was no changes in the C/N ratios even after 1000 h.