Magnetooptic disk utilizing MnBi thin films

A study has been made of a magnetooptic disk memory using MnBi thin films. The present experimental device is equipped with a MnBi medium vacuum deposited on a glass disk 139 mm in diameter and 20 mm thick, and with a rotation mechanism in which gas bearings were employed. A writing clock frequency of 1 MHz, a bit diameter of 2 μm, a bit density of 220 bits/mm, a track density of 170 tracks/mm, and reading at 5 MHz have all been achieved. In this case, the writing conditions were a writing power of 70 mW, a medium speed of 5.2 × 10³mm/s, and a pulse duration of 400 ns. The empirical relationships among the medium speed, laser power for writing, and the light pulse duration are in good agreement with the theoretical ones.