Heavy ion induced columnar defects: a sensitive probe for the 2D/3D behaviour of vortex matter in high-temperature superconductors

Heavy ion irradiation is used to create columnar defects in high-temperatur e superconductors (HTS). The heavy ion induced defects are not only very we ll controlled in shape and density, but also in the direction of the tracks with respect to the crystallographic c-axis. Pinning of the flux lines as a function of magnetic field orientation then becomes dependent on vortex d imensionality. The two-dimensional (2D)/three-dimensional (3D) behaviour of flux lines was investigated in the highly anisotropic Bi-based superconduc ting oxide. Results obtained from transport current measurements with epita xial films, measurements with small single crystals in flux transformer geo metry and muon spin rotation (mu SR) data with relatively thick crystals ar e compared. (C) 1998 Elsevier Science B.V. All rights reserved.