High density devices using permalloy propagation of wall-coded bubbles

A close-packed, field access major/minor loop device configuration has evolved from studies of the wall-coded hexagonal bubble lattice. Fully functional chips have been designed, fabricated and tested. Information is coded in the wall structure of 2.7 μm bubbles in a fully populated array of permalloy driven minor loops. A storage cell of 5.6×5.6 μm²is achieved with a 1.4 μm minimum feature. Tests of the close packed storage region show excellent propagation margin and wall state stability over the tested temperature range from 5°C to 70°C at operating frequencies to 400 kHz. Preliminary data in/data out operation has been performed at 100 kHz.