Critical current density and pinning potential in YBa2Cu3O7-δ thick films ablated from a BaZrO3-doped nanocrystalline target

We report on the pulsed laser deposition and characterization of thick (1.27 mu m) films ablated from a nanocrystalline YBa2Cu3O7-delta (YBCO) target doped with 4 wt% BaZrO3 (BZO), nYBCO/BZO. DC magnetization measurements have shown a four-to five-fold increase in the critical current density J(c) and a three- to four-fold increase in the maximum pinning force in comparison with 1 mu m thick films grown from a commercial microcrystalline YBCO target, at both 77.3 and 65 K. We have found that the frequency-dependent critical current densities J(c)(f(0)/f) estimated from susceptibility measurements are linear in a double-logarithmic plot ( where f is the frequency of the AC field and f(0) is a macroscopic attempt frequency of about 10(6) Hz), consistent with a logarithmic dependence of the pinning potential on the current density, and are again several times higher in nYBCO/BZO thick films. From the slopes of the J(c)(f(0)/f) dependences we have also estimated the values of pinning potentials in fields between 3 and 5 T.