THE BEHAVIOR OF THE INTERGRANULAR CRITICAL-CURRENT DENSITY OF POLYCRYSTALLINE, C-AXIS ORIENTED YBA2CU3O7-DELTA FILMS

The intergranular critical current density j(cJ)(T) of polycrystalline , c-axis oriented YBa2Cu3O7-delta thin films was determined at zero DC magnetic field by isothermal AC susceptibility measurements chi(h(AC) ) The shift of the intergrain peak in chi ''(h(AC)) to lower field amp litudes with increasing temperature was used to determine the temperat ure dependence of j(cJ). The obtained behaviour was confirmed by trans port critical current measurements which have been performed under sel f-field conditions. We compare our experimental data with a model for Josephson tunneling between superconducting grains in which the superc onducting order parameter has d-wave symmetry.