Garnet films for 64 Mb bubble memory devices

Garnet films of (BiSmLu)/sub 3/(FeAl)/sub 5/O/sub 12/ supporting 0.4-0.45- mu m diameter bubbles have been studied for use in 64-Mb bubble memory devices. Using CaMgZr:GGG substrates with a large lattice constant (12.498 AA), the anisotropy energy K/sub u/ can be increased to 2.5*10/sup 5/ erg/cm/sup 3/ by increasing the Sm content in the film. Consequently, the bubble diameter can be reduced to 0.4-0.45 mu m, keeping the effective anisotropy field (H/sub k/-4 pi M/sub s/) at more than 1500 Oe. For the films on GGG with a K/sub u/ value of about 1.8-10/sup 5/ erg/cm/sup 3/, the value of H/sub k/ and/or the film thickness must be decreased compared to the values for films on CaMgZr:GGG in order to reduce the bubble diameter to less than 0.45 mu m.<
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