ANGULAR-DEPENDENCE OF J(C) IN LASER-ABLATED YBCO THIN-FILMS

The field and angular dependence of critical current densities J(c) in laser ablated YBCO thin films, deposited on MgO, are investigated. Co ntributions of intrinsic pinning, due to the layer structure of the cr ystal, and of pinning due to defects are identified. It is shown that the pinning mechanism due to the crystal structure is temperature depe ndent and that a transition from a 2D superconducting state at low tem peratures to a 3D state at high temperatures occurs. In addition, syst ematic studies reveal small differences in J(c) (H parallel-to c) for films from different batches, if they are prepared under nominally ide ntical production conditions, but large differences, if the deposition temperature is lowered only slightly.