Defects in garnets suitable for magnetic bubble domain devices

A review of some of the defects that influence magnetic bubble domain motion is presented. The defects are catalogued and their origin and control are briefly discussed. A technique for staining defects by magnetic bubbles is described. The advantages of this technique over the stripe domain approach are listed. Examples of defects stained by the bubble raft technique are presented. The use of garnets for magnetic bubbles has stimulated a considerable amount of effort in understanding and eliminating magnetically active defects. Currently, the level of defects in films produced in this laboratory and elsewhere [1] range from a few to 10²defects per square centimeter. In this brief note we review and catalog the nature of defects and the status of our understanding of the origin of defects in garnet substrates and films. We shall also consider the magnetic domain techniques used for staining defects in these materials. This review is limited to defects generated during and up to steps leading to film fabrication that are common to a variety of film growth techniques. It does not include details of defects which are uniquely characteristic of a particular technique. It also does not consider defects introduced during device fabrication such as the metallurgy of the overlay or improper design of the drive pattern.