Vortex dynamics in (NiFe2O4)x/CuTl-1223 nanoparticles-superconductor composites

The effect of NiFe2O4 nanoparticles (NPs) addition on activation energy Uo(H,T) and vortex dynamics of Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase was studied. Crystal structure and phase purity of CuTl-1223 matrix and NiFe2O4 NPs were determined by X-ray diffraction (XRD). There was no substantial variation observed in lattice parameters of CuTl-1223 phase with inclusion of NiFe2O4 NPs, which indicated the settlement of these NPs across the grain-boundaries of CuTl-1223 matrix. The broadening of superconducting resistive transition in infield resistivity versus temperature curves was linked to thermally activated flux flow (TAFF) generating dissipation in the system. Overall decrease in Uo(H,T) and vortex-glass phase transition temperature (Tg) with increasing content of NiFe2O4 NPs were associated to suppression of flux pinning strength in material. The values of Tg and Tc Onset were shifted towards lower values with increasing content of these NPs, which was elaborated in the form of a vortex-phase diagram in H-T space.