Domain Walls in Thin Magnetic Ni-Fe Films

Abstract

Néel proposed a transition from the normal type of domain wall (i.e., rotation of the magnetization vector in the plane of the domain wall) to the Néel type (i.e., rotation of the magnetization vector in the plane of the film) at a certain film thickness, which is due to the thickness dependence of the magnetostatic energy. It is suggested that the cross-tie walls observed in thin Ni-Fe films with uniaxial anisotropy correspond to such a transition, in which the cross ties serve to decrease the magnetostatic energy. According to this explanation, such a structure should occur in a certain thickness range only. Experimental observations on Ni-Fe wedge-shaped films show the occurrence of the cross-tie structure in the thickness range 400-900 A, which is approximately that predicted by theory. The coercive force shows an anomaly in the same range. The energy reducing function of cross ties is also shown by the Bitter patterns near scratches in the easy-direction in negative magnetostrictive material. In a region along the scratch, the magnetization in the plane of the film is perpendicular to the original easy direction due to the local stresses and again a cross-tie structure is observed. © 1960 The American Institute of Physics.