Optimization of minor loop propagation for 8 µm period bubble memory devices

For 8 μm period bubble memory devices, minor loop propagation margins of asymmetric chevron and half disk patterns are compared under certain conditions using two kinds of garnet materials with 1.6 μm and 1.9 μm diameter bubbles. For the minor loop propagation with start-stop operation, the half disk pattern is superior to the asymmetric chevron pattern. In the 8 μm period circuit, the required drive fields for 1.9 μm diameter bubbles are remarkably reduced compared with those for 1.6 μm diameter bubbles. We found considerably large differences in propagation margins between both tracks of the minor loop. Such differences can be compensated by appropriately selecting the garnet film crystal orientation and direction of the DC in-plane magnetic field with respect to the minor loop propagation direction.