Observations Made on Domain Walls in Thin Films

Abstract

Domain walls in thin films of permalloy were previously found, by Huber et al., to frequently exhibit periodically spaced “cross-ties.” These wall structures have been studied in some detail in a variety of alloys and the model advanced by Huber et al., largely substantiated. Of some interest is the great sensitivity of the position of normal spin orientation between cross-ties to externally applied fields. A nonmagnetic overcoating on a thin film, and dark-field illumination with restricted-azimuth are methods which are valuable in such observations using the Bitter technique. Other characteristic wall configurations peculiar to thin ferromagnetic films have been observed and models have been devised for the magnetization distributions. Powder patterns have been observed on an iron film at intermediate stages of the slow switching of the film. The powder is seen to collect along lines perpendicular to the applied field prior to the formation of domains. A model based on magnetization buckling is suggested that establishes a connection between the lines that form before partial switching of the film, and the cross-ties that appear on domain walls after partial switching. Long Neel-wall segments have been observed on thin films by the Bitter technique, and by the use of fields in the plane of the film and at right angles to the wall. It has been found possible to reversibly change the direction of the magnetization in the Neel wall with such fields without introducing wall motion.