Plastic vortex creep above the second magnetization peak in Bi2Sr2CaCu2O8+delta single crystals

The analysis of the activation energy in the magnetization relaxation of Bi 2Sr2CaCu2O8 + delta (BSCCO) single crystals reveals plastic vortex creep ab ove the second magnetization peak (SMP). Above the peak field, the magnetic field dependence of the activation energy U(B) is very close to the form U (B) alpha B-1/2 and the intrinsic variation of U with the current density i s weak. The existence of a crossover from elastic to plastic vortex creep a cross the SMP of high-temperature superconductors (HTSC) seems to be a gene ral behavior, and may have important consequences on the nature of the ther mally induced vortex solid-vortex fluid transition at high magnetic fields. (C) 2000 Elsevier Science B.V. All rights reserved.