Investigation of melt-textured superconductors on the nanoscale

For the further development of the bulk, melt-processed high-T_c superconductors it is an essential issue to control the material properties on the nanoscale, as the length scale where flux pinning takes place is of the order of 10 nm. As a consequence, we need to investigate the properties of the samples accordingly on the nanoscale. Therefore, we have performed atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) scans of sample surfaces at ambient conditions which have resolved a rich variety of microstructures in the bulk samples. With the recent developments, also the (electron backscatter diffraction) EBSD technique reaches the nanometre range enabling to study the crystallographic details, especially the effect of embedded nanoparticles on the superconducting matrix. In order to obtain a direct proof of the pinning effect, the output of low-temperature STM revealing the electronic nature of the samples is studied as well. Further developments of the STM technique, e.g., employing ferromagnetic tips, may further bring informations on the flux pinning properties.