Magnetooptic studies of thin GdIG sections

Thin wafers of GdIG, made by sectioning and polishing single- and polycrystals, were studied magnetooptically to determine the parameters useful for the memory element first proposed by Chang et al. It was found that coercivity determined by means of Faraday rotation in these wafers was tenfold higher than that in bulk materials determined by conventional means. Thermal and coercivity considerations showed that a steep and wide peak in the coercivity versus temperature curve was desirable for small bit size and high writing speed. This was confirmed experimentally, and bit density of 10⁶/in²was obtained by laser beam writing on polycrystalline wafer. Bits were stable with temperature up to 50°C. They can be erased selectively by the same writing beam with reversed magnetic bias. Practical writing and reading techniques are proposed.