Vortex Lattice Structure in Bi2Sr2CaCu2O8+ delta at High Temperatures.

Abstract

The microscopic structure of the magnetic flux-line lattice (FLL) in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} superconductors was studied at temperatures up to 77K by decoration. Comparison of FLLs obtained at 55 and 4.2K shows that twisted bond defects are a manifestation of thermal fluctuations at elevated temperature. Analyses of the orientational and translational correlation functions for field and zero-field cooled lattices obtained at 55K suggest that the observed FLL is an equilibrium hexatic. These data were also used to estimate the FLL freezing temperature. {copyright} {ital 1996 The American Physical Society.}