MAGNETOOPTICAL IMAGING OF SHUBNIKOV PHASE

Among the various methods to obtain images of the Shubnikov phase in s uperconductors the high-resolution Faraday effect enables one to local (spatial resolution of about 0.8 mum) and dynamic observations of dom ain structures. In this paper the different types of flux penetration into the different kinds of high-T(c) samples (sintered materials, sin gle crystals and thin films) are presented. It is found that the obtai ned 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 pinnin g behaviour. As a new feature of the high-T(c) superconductors, it is shown that in the remanent state vortices of opposite polarity have nu cleated at the sample edges. Domain patterns of high energy heavy-ion irradiated high-T(c) samples show the advantages of a local determinat ion of the acting volume pinning forces and critical current densities . Using the capability to dynamic observations, flux creep effects can be visualised.