Direct evidence of the interaction of domains with atomic scale imperfections in GdIG

Optical observations of the interaction of domains with atomic scale imperfections are presented. Thin transparent {100} orientation wafers of GdIG are prepared from 20 mil-thick slabs by chemical polishing, and in this process etch pits develop which reveal line imperfections in the crystal. These may be individual dislocation lines or other minor structural defects. Domains are both pinned and nucleated at these lines. Interesting cooperative effects occur when a number of lines can be identified in the same sample. It is often observed, for example, that nucleation and initial domain growth take place on the same side of all the lines. In some cases a small residual domain near a line imperfection appears to influence the domain structure throughout the sample, and has the effect of favoring one saturated remanent state over the other. When the residual domain collapses, the effect disappears. Magnetostrictive stress between the domain and the rest of the sample may be responsible for this behavior.