Localized control of magnetization in LPE bubble garnet films

A new method of obtaining fine scale localized control of the magnetization,
4\piM
, for defining bubble tracks in LPE garnet films is described. It involves the deposition of a thin film of silicon on the garnet surface and then annealing in oxygen, or inert gas, at moderate elevated temperatures. Under the silicon,
4\piM
decreases by large amounts upon annealing. These reductions in
4\piM
, together with photolithographic techniques, can be used to define tracks for bubble propagation. Bubble propagation bit rates up to 1 MHz have been obtained in tracks
\sim6 \mu
m wide. A mechanism to explain the effect is proposed involving a lowering of the relaxation time for transfer of gallium ions from octahedral to tetrahedral sites due to the presence of local oxygen defects, or Fe
²⁺
, produced in the garnet film by removal of oxygen at the heated garnet-silicon interface. In areas not covered by silicon,
4\piM
remains unchanged.