Direct study of magnetic flux penetration and trapping in HTSC.

  Abstract:
A method for visualization of the magnetic flux penetration and trapping in high-temperature superconductors (HTSC) using magneto-uniaxial ferrimagnetic films is described. The difference in the character of these processes in a number of materials (HTSC single crystals, films and ceramics) is studied. Specific features of remagnetization of Tl₂Ba₂CaCu₂O_x  and YBa₂Cu₃O_7-d  single crystals in the superconducting state which do not fit the simple Bean model are found. Temperature dependences  of the local magnetic susceptibility are measured in different sites of the samples. Non-uniformities of their superconducting properties related to structural defects are revealed.