Two-step transition towards the reversibility region in Bi2Sr2CaCu2O8−δ single crystals

Abstract

We have performed magnetization measurements on Bi2Sr2CaCu2O8−δ single crystals in the c^ crystallographic direction for fields from 2 Oe up to 700 Oe. The results strongly suggest that the reversible thermodynamic region is achieved after the vortex flux structure shows an abrupt transition at a temperature lower than that determined by the irreversibility line.