Ferromagnetic domains in EuS investigated by low-temperature Lorentz microscopy

Thin films of EuS, prepared by electron beam evaporation, were investigated by Lorentz microscopy in a special low-temperature object stage. In the thermally demagnetized state of an isotropic film, a multidomain configuration is observed with the smallest detectable domain size being about 200 nm. In the ac-demagnetized state, the domain configuration is similar to the configuration during a magnetization reversal. The magnetization reversal in an isotropic film starts by nucleation of small domains at inhomogeneities in the film, mostly at the edges, and by the growth of the nuclei. The domain configuration is strongly influenced by mechanical stress. The mechanical stress has an effect on the magnetization reversal of EuS similar to a field-induced anisotropy in NiFe films. The walls in EuS films down to a film thickness of 7 nm are Bloch walls.