The formation of remanent states in permalloy overlays

Experiments are described which reveal the behaviour of domains in 16μm-period permalloy overlays. Components often found in commercial bubble devices were investigated. For each component the magnetization process exhibits hysteresis and the formation of remanent domain configurations if the applied field exceeds a critical value, H
s
. Some details of these irreversible processes are given. The dependence of H
s
on element geometry and thickness is investigated. In quasi-static rotating fields (exceeding H
s
) remanent states often persist for a large part of the field cycle. This may influence the behaviour of a bubble device.