The formation and structure of cylindrical magnetic domains in thin cobalt crystals

Arrays of cylindrical domains, “bubbles”, in basal foils of cobalt may be produced by the application of magnetic fields along the c-axis. The bubbles are observed directly in the electron microscope and coexist with plate domains in fields up to 15 kOe. Two types of bubbles exist identified by the presence or not of constituent Bloch lines. The comparative energies of the two types of bubbles are calculated including a detailed theoretical treatment of the Bloch lines. Possible nucleation mechanisms responsible for the formation of both sorts of bubbles are discussed.