Orientation dependence of propagation margin of 1-μm bubble contiguous-disk devices—Clues and cures

The operating margins for bubble propagation along ion-implanted contiguous-disk devices are found to depend upon the orientation of the propagation track with respect to the tridirectional crystalline symmetry of the implanted garnet layer. Continuous disk propagation structures provide bubble tracks on each side of the structure. Depending upon orientation both tracks may have equally good propagation margin, or one track may be characterized as super while the other is bad. Studies of charged wall configurations using Ferrofluid colloid show distinct differences in wall behavior associated with the good, bad and super tracks. Annealing and removal of the implantation-protected Au patterns tend to improve, but not cure, the bad tracks. One solution is to orient the orthogonal major-minor loop tracks at 15° to an easy stripout direction so that all tracks propagate acceptably well; however, superior performance can be obtained by a parallelogram array with all tracks parallel to an easy stripout direction.