Abstract
The addition of magnetic Co0.5Zn0.5Fe2O4 nanoparticles to the superconducting Cu0.5Tl0.5-1223 phase has been used to investigate the electrical resistivity behavior of the composite above the superconducting transition temperature T-c. This was studied according to the opening of spin gap and fluctuation conductivity. The results indicated that the pseudogap temperature (T*) and superconducting fluctuation temperature (T-scf) change by increasing the addition of Co0.5Zn0.5Fe2O4 nanoparticles. It was found that T* is related to hole carrier concentration P and it also depends on the antiferromagnetic fluctuation affected by magnetic nanoparticles. The excess-conductivity analysis showed four different fluctuation regions started from high temperature up to T-c, and they were denoted by short wave (sw), two-dimensional (2D), three-dimensional (3D), and critical (cr) fluctuations. The crossover temperature between 3D and 2D (T3D-2D) in the mean field region was decreased by increasing the addition of Co0.5Zn0.5Fe2O4 nanoparticles, in accordance with the decrease in T-scf with x. The coherence length at 0 K along c-axis xi(c)(0), effective layer thickness of the 2D system d, and inter-layer coupling strength J were estimated as a function of Co0.5Zn0.5Fe2O4 nanoparticle addition. Moreover, the thermodynamics, lower and upper critical magnetic fields, as well as critical current density have been calculated from the Ginzburg number N-G. It was found that the low concentration of Co0.5Zn0.5Fe2O4 nanoparticles up to x = 0.08 wt% improves the superconducting parameters of Cu0.5Tl0.5-1223 phase. On the contrary, these parameters were deteriorated for (Co0.5Zn0.5Fe2O4)(x)/Cu0.5Tl0.5-1223 composite with x > 0.08 wt%.