Analysis of fluctuation conductivity in Y-=SUB=-0.5-=/SUB=-Cd-=SUB=-0.5-=/SUB=-Ba-=SUB=-2-=/SUB=-Cu-=SUB=-3-=/SUB=-O-=SUB=-7-delta-=/SUB=-

Abstract

A study was made of the influence of substitution of up to 50% of yttrium for cadmium in YBa2Cu3O7-delta polycrystals on the mechanism of formation of excess conductivity. It has been established that such a substitution led to a significant increase in the resistivity of Y0.5Cd0.5Ba2Cu3O7-delta, and the value of the critical transition temperature Tc to the superconducting state decreases. The mechanism of formation of fluctuation conductivity (T) near Tc is considered within the framework of the Aslamazov-Larkin theory. The Ginzburg temperature, the critical temperature in the mean field approximation, and the 3D-2D crossover temperature were determined. It is shown that the doping of YBa YBa2Cu3O7-delta with cadmium leads to an increase in the coherence length along the c axis by a factor of 3.2. An analysis of the excess conductivity of the Y0.5Cd0.5Ba2Cu3O7-delta sample within the framework of the local pair model made it possible to determine the temperature dependences of the pseudogap and its maximum value. Keywords: superconductivity, fluctuation conductivity, pseudo-gap, coherence length.