Nanoscale magnetic domain structures in epitaxial cobalt films

We have analyzed the magnetic domain structure in high quality molecular beam epitaxy (MBE) grown (0001)-hcp cobalt films of thicknesses varying from 10 to 500 nm for which the magnetic domain width is of the order of the film thickness. As the thickness of the film is increased, the magnetization turns from fully in plane (10 nm) to fully out of plane (50 nm) over a relatively large thickness range. Above 50 nm, the local domain imaging by magnetic force microscopy (MFM) together with overalI magnetization measurements confirm the characteristic multidomain structure with perpendicular orientation predicted by Kittel. The periodicity of domains is then described by a root d law (where d is the film thickness) thar leads to the determination of domain wall energies. The occurrence of magnetic bubbles and periodic stripe patterns is visualized by variable field MFM.