Complementary permalloy bubble propagation structure

Bubble propagation has been achieved in a novel permalloy structure made up of a pattern and its complement. The pattern is defined by a step in the spacer on top of which the permalloy is deposited leaving the permalloy in two levels. Bubbles are propagated under the influence of the fringe field generated at the permalloy step by a rotating in-plane field. The fabrication of the devices is as follows: A spacer layer of SiO2(3000Å) is first deposited followed by the application of photoresist (1.5μm). The photoresist is patterned such that undeveloped resist is left in the area of low permalloy. A layer of Schott glass (4000 to 6000Å) is deposited over the wafer followed by lifting off the photoresist. This leaves Schott glass layer in the area of high permalloy. A permalloy layer (15OO to 2500Å) is deposited over the entire device area. Devices of 10μm period and 2μm minimum feature were fabricated (see photo) and tested. Propagation margins >10% were obtained with 35 to 50 Oe drive fields.