Flux-line lattice dynamics and irreversibility line in single crystalline Bi2Sr2CaCu2O8+ delta

Abstract
High-field magnetisation measurements up to 38 T have been performed on single-crystalline Bi2Sr2CaCu2O8+ delta in order to investigate the irreversible behaviour associated with the flux line dynamics. It was found that the irreversible magnetisation vanishes asymptotically at high fields well below Bc2. As temperature is increased, above approximately 40 K, the magnetisation essentially become reversible. Critical currents Jc and volume pinning forces Fp were calculated and compared with the results of YBa2Cu3O7- delta . The irreversibility line deduced from the present measurements as well as from other techniques is discussed in terms of a possible boundary, above which superconducting phase fluctuations play a dominant role for the dissipation.