Critical current density of Ag-doped Y-Ba-Cu-O superconductors in low magnetic fields

The variation of critical current density of silver-doped Y-Ba-Cu-O superconductors in low magnetic fields has been investigated. A semilog plot of the field dependence of the critical current density reveals a well-defined field value H'_c characteristic of a crossover between regions dominated by the inter- and intra-granular effects. Below H'_c, the normalized critical current density with different silver contents can be expressed as a universal function of the average magnetic flux in the weak link region. Increasing the silver content from zero to 15 mole percent corresponds to a monotonic increase of the screening supercurrent in the supercinducting material.