Nearly isotropic propagation of 0.5 micrometer bubbles in contiguous disk devices

"Good" and "bad" ion implanted bubble propagation tracks of various shaped patterns (snake, diamond, circular and triangular shapes) were fabricated on garnet films for 0.5 µm bubbles with nearly isotropic magnetostriction. Quasistatic bias margin measurements show great improvement of bad track margins for all pattern shapes. The best overlapping bias margins were obtained from 2.5 µm period diamond shaped patterns, which show a 30 Oe minimum drive field and 78 Oe margin width at 50 Oe drive. On the other hand, snake patterns exibit the best "good" track margin with a minimum drive of 25 Oe and a margin width of 78 Oe at 50 Oe drive, but show somewhat inferior "bad" track margins. It was found that "bad" track margins of snake patterns are especially sensitive to ion implantation conditions and the propagation pattern cusp shape. By carefully adjusting ion implantation conditions (implantation energy and dosage) and the pattern cusp shape, nearly isotropic propagation was achieved for all propagation pattern shapes tested.