Vortex pinning regimes in thin films of YBa2CU3O7-delta

The field dependence of the superconducting current density j(s)(B) and the pinning energy U-c(B) in thin films of YBa2Cu3O7-delta indicates three dif ferent pinning regimes. At low fields, mu H-0 < B* <approximate to> 0.7n(d) Phi (0) (n(d) is the density of dislocations), j(s)(B) is constant and U-c = 600 K at T = 0 for all YBa2Cu3O7-delta films, independent of the density of dislocations. This is much lower than the pinning energy of a vortex in a single dislocation, for which U-c approximate to 6000 K. At intermediate fields, B* < <mu>H-0 < 0.5 T, a sharp decrease of U-c is observed. For <mu> H-0 > 0.5 T, U-c(B) is constant again, with U-c(B) approximate to 80 K for sputtered films and U-c(B) approximate to 200 K for laser ablated films.