RELIABLE PROPAGATION OF MAGNETIC-BUBBLES WITH 8-MU-M PERIOD ION-IMPLANTED PROPAGATION PATTERNS

Ion implanted propagation patterns for magnetic bubble devices provide an approach to higher density through relaxed photolithography. At the same time, the drive field requirements may be reduced, with respect to Permalloy based field access devices. Propagation is studied in the present work at 8 μm period in YSmLuCaGe films. Profiling by relative etch rate and by wafer curvature has led to 80/Ne/1-2E14+270/Ne/2E14+130/H2/2E16 implantation conditions. Bias field margins vs drive field for 27-step loops with neighbors on 2 λ centers and in orthogonal orientations on the wafer are presented to demonstrate the feasibility of major-minor loop organized chips. Crystal symmetry effects do cause the margins for differently oriented loops to be different in the present material, however. The overlap bias range is about 20 Oe extending downward from free bubble collapse. The minimum drive at 40°C appears to be about 35 Oe. Bias margins at 40 Oe drive taken over the temperature range 0-80°C show no anomalies for either orientation. Long term retention has been demonstrated for up to (10)8 cycles at 50 kHz, 40 Oe drive and 40°C.