Magneto-optical imaging of Shubnikov phase

Among the various methods to obtain images of the Shubnikov phase in superconductors the high-resolution Faraday effect enables one to local (spatial resolution of about 0.8 μm) and dynamic observations of domain structures. In this paper the different types of flux penetration into the different kinds of high-T_c samples (sintered materials, single crystals and thin films) are presented. It is found that the obtained domain structures of single crystalline materials depend strongly on the geometry of the samples. The possibility to local observations allows to study the influence of various microstructures on the pinning behaviour. As a new feature of the high-T_c superconductors, it is shown that in the remanent state vortices of opposite polarity have nucleated at the sample edges. Domain patterns of high energy heavy-ion irradiated high-T_c samples show the advantages of a local determination of the acting volume pinning forces and critical current densities. Using the capability to dynamic observations, flux creep effects can be visualised.