Six micrometer period wide-gap permalloy magnetic bubble devices

This report describes the progress made toward the goal of developing a 1 Mbit bubble memory chip, based on a 6 μm period wide-gap permalloy technology. Characterization of the functions showed that the guard-rail, generator, swap, write-line, read-line and after several revisions, the replicator and the expander-detector performed acceptably in preliminary testing. Full longevity qualification was not conducted. A data-every-cycle capability was also designed into the chip. A major problem that remained was a poor yield of operating minor loops. Several investigations were initiated to solve the problem of low minor loop yield. A dual-spacing process, which allows the minor loop propagation elements to be more tightly coupled to the garnet film was developed. Several new propagate structures, intended to be more tolerant of small defects (either in the epi-film or in the patterning of the circuit), were also conceived.