Scaling of permalloy propagators for bubble devices

The extent to which field access permalloy bubble devices can be scaled in density depends fundamentally on the scaling characteristics of the basic propagator. The effects of bubble film parameters and thin film thicknesses when the minor loop propagator period is varied are measured for bit loading and minimum drive. Various asymmetric chevrons propagators with period sizes ranging from 5.5 to 7.5 μm, with stripe widths varying between 1.2 and 2.8 μm, and with spacer thicknesses covering 1500 to 5000 Å are compared. An accurate comparison was obtained by placing different period sizes and propagator designs on the same wafer. Propagation bias field and drive field margins are reported with start/stop operation and data patterns of increasing complexity. Data shows that material and fabrication requirements should be based on margins characteristic of fully loaded bubble patterns rather than on performance corresponding to lightly loaded patterns.