Composite magnetic thin films consisting of layers of different magnetic materials in close molecular contact with one another are studied. Because of ferromagnetic exchange coupling between spins, the magnetization in the neighborhood of the interface of the layers is expected to rotate continuously as in Bloch walls. The experimental magnetization curve of an extremely soft magnetic layer on an extremely hard magnetic layer agrees well with the theoretical curve based on such rotation models. Drastic deformations in critical switching curves from the asteroid of conventional uniaxial films, improvement in nondestructive reading characteristics, and existence of a new switching mode which is dependent upon the sequence of external magnetic fields are also expected from a theory based on a lumped‐constant approximation to the continuous rotation model. All of these theoretical predictions have been confirmed by experiments using electroplated composite films.