Excess conductivity in Cu_(0.5)Tl_(0.5)Ba_2[Ca_(2-y)Mg_y](Cu_(0.5)Zn_(2.5))O_(10-δ) superconductor

摘要

Synthesis and characterization of Cu_(0.5)Tl_(0.5)Ba_2[Ca_(2-y)Mg_y](Cu_(0.5)Zn_(2.5))O_(10-δ) (y=0, 1.0, and 1.5) superconductor with 0%, 50%, and 75% Mg-doping at the Ca sites are reported. The samples were synthesized by solid-state reaction and characterized by X-ray diffraction (XRD), dc-resistivity (p) and fluctuation induced conductivity (FIC) analysis. The zero resistivity critical temperature (T_c(R=0)} was decreased with the increase of Mg-doping at Ca sites. The microscopic parameters such as the cross-over temperature (T_o), zero temperature coherence length {ξ_c(0)} and interlayer coupling (J) were deduced from FIC analysis. According to Aslamazov Larkin equations, a distinct cross-over temperature [T_(o1)]from three-dimensional (3D) to two-dimensional (2D) fluctuation induced conductivity regions was observed in all samples. Another cross?over temperature [T_(o2)] from 2D to zero-dimensional (0D) fluctuations was also witnessed. FIC analysis revealed the deterioration of superconductivity with increased Mg-content.