Critical current density and dynamical relaxation. rate below the matchingfield in thin films of YBa2Cu3O7-delta

We studied the superconducting current density j(s)(B, T) and dynamical rel axation rate Q(B, T) of laser ablated thin films of YBa2Cu3O7-delta with va rious dislocation densities (n(disl) similar to 7 - 70 mu m(-2)). In these films dislocations act as strong pinning centers like columnar defects in h eavy ion-irradiated crystals. The matching field clearly manifests itself i n a constant j(s)(B) similar to 5.10(11) - 1.10(12) Am-2 at T = 4.2 K and m u(0)H less than or similar to 0.7.B-Phi and a constant Q(B). In contrast to irradiated crystals, in films we do not observe a peak: in the relaxation rate Q versus T below the matching field B-Phi equivalent to n(disl) . Phi( 0) Instead, in thin films Q(T) increases monotonously with increasing tempe rature. We conclude that the influence of vortex-vortex interactions in thi n films is greatly reduced due to the non-random distribution of pinning si tes and the low matching field.