High-resolution observation of magnetization processes in 2 μm × 2 μm × 0.04 μm permalloy particles

The magnetization process in an array of 2 μm × 2 μm × 0.04 μm permalloy particles fabricated on a 100 nm carbon membrane was investigated by means of high-resolution Lorentz microscopy and electron holography in magnetic fields parallel and perpendicular to the film surface. For perpendicular fields, the magnetization reversal was found to begin with the nucleation of a vortex which gradually transformed into a closure domain configuration. At the remanent state, the flux closure was achieved with the generation of a new type of doubled domain wall.