Fabrication of ``Bubble''-Propagating Circuits by Electroless Deposition of Nickel-Cobalt-Phosphorous

Propagating cylindrical magnetic domains, or ``bubbles,'' in garnet platelets is accomplished by placing a periodic thin-film magnetic circuit, such as T bars, in contact with the platelet and applying an in-plane rotating field to alternately magnetize different segments of the circuit element. A process has been developed for fabricating high-density bubble-propagation circuits utilizing electroless deposition of an Ni–Co–P alloy. Circuits have been deposited both on glass substrates and directly on garnet platelets cemented to glass substrates. The highest density, 2.8×106 bits/in.2, has been achieved in a 0.6-mil period 1000-bit Y-bar shift register. Linewidths of 2 μ are currently attainable and appear limited by the resolution of available photolithographic techniques. The process results in rapid turn-around time, the materials are inexpensive, and no sophisticated equipment is necessary for the plating process.