Columnar tilt and vortex stress in superconducting thin films of NdBa2Cu3O7-delta: Magnetization critical current-density measurements

摘要

C-axis-oriented NdBa2Cu3O7-delta thin films (thickness similar to2000 Angstrom) on LaAlO3 substrates have been prepared and irradiated with Ag+14 (200 MeV) ions at different inclinations (theta(d)=0degrees, 15degrees, 30degrees, and 45degrees) to the c axis. Magnetization-field hysteresis loops have been obtained on pristine and irradiated thin films at two different temperatures in applied magnetic fields up to 5 T. Estimates of the critical current density J(c)(H,theta) and the volume pinning force F-p(H,theta) from the magnetization data reveal a strong dependence on track inclination. An increase and a subsequent saturation in F-p(H,theta), instead of the usual Gaussian peak around the equivalent matching field, B-phi, is observed. It is suggested that this dependence of J(c) (or F-p) on theta(d) is a consequence of the effective modification of vortex pinning by tilted columnar defects. (C) 2004 American Institute of Physics.