Characteristics of critical current density and weak links in an YBa2Cu3O7−δ superconducting thin film

Abstract Temperature and magnetic field dependences of critical current have been carried out on an YBa 2 Cu 3 O 7−δ superconducting thin film. The critical current I c ( t ) = I c (0) (1− t ) 2 , which is just like that of a network constructed by ideal S-N-S junctions. The critical current behaves in different ways with H parallel to the film surface and H perpendicular to the film surface, and this is related to weak links between grains. The critical field for breaking a major part of the weak couplings is about 80 Oe, and the lower critical field of grains determined here is about 136 Oe.