L. Miu et al., Crossover from elastic to plastic vortex creep across the second magnetization peak of high-temperature superconductors, PHYS REV B, 62(22), 2000, pp. 15172-15176
We investigated the relaxation of the irreversible magnetization of YBa2Cu3
O7-delta, Pb2Sr2Y0.53Ca0.47Cu3O8, and Bi2Sr2CaCu2O8+delta single crystals w
ith significant quenched disorder in the region of the second magnetization
peak. It was found that for an applied magnetic held between the onset fie
ld and the peak field the relevant current-density dependence of the activa
tion energy exhibits a sudden change, which can be interpreted as a crossov
er from elastic to plastic vortex creep. The evolution of this change with
magnetic field illustrates the increase of the collective pinning barrier b
etween the onset field and the peak field. The observed increase of the col
lective pinning barrier is Limited by the plastic barrier at the peak field
. This appears to be a general behavior, and may have important consequence
s on the interpretation of the thermally induced vortex phase transition at
high magnetic fields.