Thermal Conductivity of Tl(2)Ba(2)CuO(6+delta) and Fluctuation Diamagnetism of YBa(2)Cu(3)O(6+x)

Abstract

The increased contribution of the fluctuation signal to the magnetization over a wide temperature range is clearly evident in the more anisotropic samples. Within the anisotropic-effective-mass 3D-XY model, the change in anisotropy with reduced transition temperature is directly related to the magnitude of the fluctuation signal at T$\sb{\rm c}.$ It is found that both the ratio $\gamma$ = (m$\sb{\rm c}$/m$\sb{\rm ab}$)$\sp{1/2}$ and the in-plane coherence length increase by a factor of two as the transition temperature is lowered from 92 K to 70 K, with little change in the c-axis coherence length.