Y3Fe5O12 Nanoparticles as Efficient Pinning Centers and Temperature Dependence of the Critical Current in YBa2Cu3O7-δ Nanoparticles

Magnetic measurements have been reported in nanosized YBa2Cu3O7-δ (YBCO) cylindrical tablets doped with different proportions of Y3Fe5O12 (YIG) nanoparticles. X-ray diffraction and magnetization measurements have been achieved to characterize samples and study the influence of temperature T, applied field H, and added YIG on the intergranular critical current JC. The field has been applied perpendicular to the tablet. Temperature exponential decay of JC in YBCO nanoparticles has been observed and analyzed in the collective and correlated model framework. A two-current model has been proposed: the low-T region behavior has been attributed to the trapping effectiveness of ferromagnetic and superconducting nanoarea interfaces. In the high-T region, there are many ferromagnetic traps to ensnare a very small number of vortices leading to a flexing of JC decrease vs. T and to very low values of JC. Field dependence of JC of many tablets of YBCO with different YIG quantities has shown an optimum enhancement of JC for 0.5% of YIG in weight.