Excess conductivity analysis and infrared absorption spectroscopy of Mg-doped TlBa₂Ca₂Cu₃O₁₀−δ superconductor

Abstract

Fluctuation induced conductivity (FIC) analysis on dc resistivity versus temperature data of as-prepared and oxygen post-annealed TlBa₂(Ca₂–yMgy)Cu₃O₁₀–δ (y = 0, 0.25, 0.5, 0.75, 1.0) superconductor samples are carried out by using Aslamazov–Larkin model for excess conductivity. The microscopic parameters such as zero temperature coherence length along c axis {ξc(0)}, interlayer coupling (J), intergrain coupling (α), critical exponent (λ) and dimensionality of superconducting fluctuations are calculated with the help of aforementioned model. The crossover temperature (T₀) is shifted towards higher temperature values with the increase of Mg contents up to y = 0.5 and then start to decrease but still remains greater than those values of undoped samples. The increase in ξc(0) and J after Mg-doping at Ca sites shows the improvement of interplane coupling in TlBa₂(Ca₂–yMgy)Cu₃O₁₀–δ samples. The appreciable change in all the microscopic parameters extracted from the FIC analysis indicates the optimization of oxygen in all the oxygen post-annealed samples. The increase in relative intensity of almost all the oxygen modes indicates the oxygen diffusion in the unit cell after oxygen post-annealing. The diffusion of oxygen can take place at intergranular sites along with intragranular sites, which increases the grains size, intergrain connectivity and carrier density in CuO₂ planes.