A 4Kbit bubble memory chip using X-bar propagation patterns

The design and operation margins of a bubble memory chip 2,8 mm × 2,1 mm with 32 minor loops of 128 bits of storage capacity each are described. In a special package, designed for test purposes and containing the drive field coils and a variable bias magnet system, signals up to 10 mV are generated by bubbles of 6 μm diameter in a thin film detector. The X-bar propagation works well up to 500 kHz using garnets having the composition Y1,6Sm0,4Ca1Fe3,9Ge1Si0,1O12. Also the transfer is performed by special X-bar transfer gates.