A new magnetooptic effect related to non-uniform magnetization on the surface of a ferromagnet

Evidence for a new magnetooptic effect is found in domain observation on magnetic materials. The new effect is observed typically at perpendicular incidence and manifests itself as an unexpected alternating domain boundary contrast not related to the internal structure of the walls. It is visible directly in the polarizing microscope under favourable conditions, but can be more clearly demonstrated by utilizing the now well established digital difference technique. The effect proves to be highly symmetric, depending only on the domain magnetization difference direction and the boundary orientation relative to the polarization direction. A formal description in terms of a magnetic birefringence proportional to certain linear combinations of the components of the magnetization gradient tensor is possible. In addition to this a report is given about a related effect involving gradients in the perpendicular magnetization, and about the first observation of magnetic domains by linear magnetic birefringence (the Voigt effect) in reflection.