The domain structures observed in low magnetization compositions of iron garnet films grown by chemical vapor deposition (CVD) on rare earth gallium garnet substrates are consistent with a recently‐developed stress model for epitaxial films1. By utilizing lattice matching, bubble domains have been formed in positive magnetostriction materials in compression as well as negative magnetostriction materials in tension. The film/substrate mismatch characteristics can be evaluated by comparing domain structures, X‐ray measurements of the strained lattice spacings, and the predictions of the stress model. Requirements and restrictions on the mismatch of film/substrate lattice constants and thermal expansions are discussed for the iron/gallium garnet system.