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

C-axis-oriented NdBa2Cu3O7-δ thin films (thickness ∼2000 A ring ) on LaAlO3 substrates have been prepared and irradiated with Ag+14 (200 MeV) ions at different inclinations (θd=0 deg., 15 deg., 30 deg., and 45 deg.) 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 Jc(H,θ) and the volume pinning force Fp(H,θ) from the magnetization data reveal a strong dependence on track inclination. An increase and a subsequent saturation in Fp(H,θ), instead of the usual Gaussian peak around the equivalent matching field, Bφ, is observed. It is suggested that this dependence of Jc (or Fp) on θd is a consequence of the effective modification of vortex pinning by tilted columnar defects