Domain Walls in Thin Ni-Fe Films

Observations of domain walls in Ni-Fe films as a function of thickness demonstrate the strong influence of magnetic stray fields on the wall structure, hence on the coercivity for wall motion. In order to reduce the stray-field energy, the Bloch walls in films thicker than 1000 A are subdivided into sections with alternating polarity which are separated by Bloch lines. In thinner films, the domain walls are of the Néel type. The position of Bloch lines in such walls is indicated by crosswalls. The motion of Bloch lines in an applied field can be observed particularly easily on scratches in negative magnetostrictive material; such scratches display properties corresponding to Néel walls. Crosswalls are also present at the ends of domains and around holes in the film material. A crosswall is distinguished from ordinary domain walls by the continuous change of the angle of magnetization along both sides of it.