Trapped magnetic flux in YBa2Cu3O(7-delta) superconductors

Simultaneous measurements of the magnetic field dependence of the critical current density and the magnetization of yttrium barium cuprate superconductors have shown the presence of significant residual magnetic fluxes even in zero applied field. These can be sufficient to leave the material in the mixed state and hence can seriously influence the interpretation of the observed electrical and magnetic properties. This trapped flux appears to be associated with a magnetic field component threaded through the intergranular regions, whose motion is inhibited by circulating currents flowing in the granular system surrounding the field and preserved through the weak-link coupling. Once this coupling is destroyed, the field can move more freely.