Critical current measurements in YBa2Cu3O7-δ/Sr, Fe samples

The critical currents in YBa2Cu3O7-δ and Sr- (for Ba) and Fe- (for Cu) substituted samples were measured by 4-probe resistive measurements and magnetization experiments. The critical current density Jc is related to the underlying microstructure, which differs for all three systems. The field dependence of Jc and the comparison of the V-I curves measured in the conventional and force-free configuration gives an indication on the effects which determine the critical currents in the superconducting state of sintered bulk samples.