Incoherent rotations in thin films with in-plane anisotropy

Abstract

The hard axis magnetization process in thin ferromagnetic films has been investigated by Lorentz electron microscopy. At the onset of an external magnetic field the local magnetization vectors of the individual domains rotate incoherently. To describe these rotations an internal field is introduced. The magnitude of this field and its evolution during the magnetization process are calculated in terms of experimentally measured directions of local magnetization. The internal field increases as the domains appear, attaining two extreme values and then gradually vanishes close to saturation. Its maximum value depends on the width of stripe domains arising when the film is magnetized along the hard axis. The internal field is the main factor determining the shape of the hysteresis loop.