Dependence of the ferromagnetic domain width on the thickness of cobalt foils

Previous measurements of the dependence of the domain width on the crystal thickness of cobalt are extended down to a thickness of 400 Å by means of the Lorentz transmission electron microscopy. In crystals thinner than 4 μm the domain width is proportional to the square root of the thickness as expected for the simple plate domain structure (Kittel type) without surface domain structure. However, the experimental dependence is shifted slightly compared to the theoretical curve.