Excess conductivity analysis for Tl 0.8Hg 0.2Ba 2Ca 2Cu 3O 9−δ substituted by Sm and Yb

Abstract

A series of superconducting samples of type Tl 0.8Hg 0.2Ba 2Ca 2− x R x Cu 3O 9−δ, where R=Sm and Yb with 0 ≤ x ≤ 0.15 , were prepared in a sealed quartz tube via a solid-state reaction technique. The electrical resistivity ρ ( T ) was measured as a function of temperature using the conventional dc four-probe technique. The fluctuation conductivity Δ σ , above the superconducting transition temperature T c , was analyzed as a function of temperature using the Aslamazov and Larkin model. It exhibits five different fluctuation regions namely critical (cr), three-dimensional (3D), two-dimensional (2D), one-dimensional (1D) and short-wave (sw). The zero-temperature coherence length, the effective layer thickness of the two dimensional system, the wire cross-sectional area for one dimensional systems and the inter-layer coupling strength were estimated as a function of the substitution-content x . Furthermore, the thermodynamics critical field, lower critical magnetic field, upper critical magnetic field, critical current density and Fermi energy are calculated from the Ginzburg number.