Order in the domain structure in soft-magnetic thin-film elements: a review

The domain structure and its development in thin plane-parallel soft-magnetic elements have been investigated from both the experimental and the theoretical point of view. The experimental observations for verifying the predictions have been realized by means of the Bitter, Kerr, and Lorentz techniques. A self-consistent domain theory, based on micromagnetic principles, is unfolded for two-dimensional solenoidal magnetization distributions present in ideally soft-magnetic thin-film objects that are rectangular cylinders. The solenoidality implies that both the external field and the conduction currents are taken as zero. Two types of domain structures are distinguished: the basic structures in simply connected regions and the parallel configurations in special types of multiply connected regions - the parallel regions. A decomposition of the area of the object into disjunct subregions, either simply connected or of the parallel type, whose union completely covers the object, is put forward. A procedure for constructing all feasible parallel regions is presented. The M distribution is studied on a local scale, at which the requirement of solenoidality is dropped; i.e., external fields and conduction currents are allowed. The concept of the domain-wall cluster is introduced in order to obtain the maximum information about the M configuration in the entire object.