Bubble domain propagation and sensing

A review is given of the state of the art of propagation and sensing means for bubble domain devices. In the past three years, bit density has increased a thousandfold, from 2000 bits/in
²
to 2 million bits/in
²
. Drive field requirements and sensor efficiency have remained nearly constant. A unified theory of device design is only now beginning to appear, but experimental evidence so far suggests that devices with submicron bubbles and 100 million bits/in
²
are only a matter of time.