Two samples of single phase thallium-calcium-barium-copper-oxide were prepared using a precursor matrix technique. The resistivity of these samples was determined from 300 K to the temperature of zero resistance, Tzero, using the Montgomery technique. The room temperature resistivity of sample 2 was approximately seven times the room temperature resistivity of sample 1. From these measurements it was found that the temperature dependence of the fluctuation-induced excess conductivity in both the samples was in agreement with the Aslamazov-Larkin expression for three dimensional fluctuations. © 1989.

Sankaranarayanan V

Department Of Physics

H. Krishnan

Ceramic materials

High temperature superconductors

Oxide superconductors

THALLIUM CALCIUM BARIUM COPPER OXIDES

Thermodynamic fluctuations

Superconducting materials

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IIT Madras

Fluctuation induced excess conductivity in Tl2CaBa2Cu2O8

Physica C: Superconductivity and its applications

Fluctuations in phase across the weak links in a granular superconductor contribute to the excess conductivity below Tm, the temperature at which the plot of temperature derivative of electrical resistivity against temperature shows a maximum. In a narrow range of temperature above T∞ (the temperature at which the resistivity at which the resistivity becomes zero), the excess conductivity, Δσ = [σ(T) - σ(Tm)], is expected to vary as (T-T∞)-γ. In this work, resistivity measurements on CaREBaCu3O7-y (RE=La, Sm), Ag coated YBa2Cu3O7-y, Tl2CaBa2Cu2O8 and YBa2Cu3-xZnxCu3O7-y (x=0.05, 0.075, 0.1 and 0.15) in the paracoherence region are reported. Analysis of the data indicates the excess conductivity in this region is better described by the critical exponent y = 1.33. From an analogy between the tunneling Hamiltonian in the granular material and the Hamiltonian for an XY ferromagnet one expects the critical exponent, γ, to be the same as the critical exponent for susceptibility in the ferromangetic case. © 1992.

Excess conductivity studies in the paracoherence region in high- temperature superconductors

We have measured the electrical resistivity of Tl2Ca1Ba2Cu2O8-∂ to establish the dimensionality of the fluctuations enhanced conductivity σp. We find the derivative technique (proposed by testardi et al and later used by Kim et al) gives a less ambiguous value of the exponent of σp. The fluctuations appear to be two dimensional in nature over the temperature range 93 &lt; T &lt; 300K despite the sample having a lower Tc (84K for ρ{variant}=0) due to degradation/loss of oxygen. © 1990.

Solid State Communications

Paraconductivity of Tl2Ca1Ba2Cu2O8-∂

Journal of Applied Physics

Method for Measuring Electrical Resistivity of Anisotropic Materials

Physica C: Superconductivity

Excess electrical conductivity in polycrystalline Bi-Ca-Sr-Cu-O compounds and thermodynamic fluctuations of the amplitude of the superconducting order parameter

Modern Physics Letters B

EVIDENCE FOR ANOMALOUS FLUCTUATIONS IN SUPERCONDUCTING Bi1.75Pb0.25Ca2Sr2Cu3O10

Evidence for K-substitution in the Tl-sites of superconducting Tl2CaBa2Cu2Oχ: Neutron diffraction studies

Physical Review B

Anomalous in-plane paraconductivity in single-crystal YBa2Cu3O7

Journal	Physica C: Superconductivity and its applications
ISSN	09214534
Open Access	No