Order-Disorder Transition And The Zero-Dimensional Vortex Pinning Regime In Bi2sr2cacu2o8+Delta

We make a comparative study between the ab plane's dc critical current and the ac transverse magnetic permeability mu (perpendicular to) in the Campbell limit for optimally doped and overdoped Bi2Sr2CaCu2O8+delta samples. We focus attention on the low-temperature region [T/T-c(0) < 0.25], where the transition to the zero-dimensional Larkin limit is detected by the critical current as well as by a rapid change of the Labusch parameter with temperature. The order-disorder transition, characterized by the second peak in magnetization, disappears in the presence of this zero-dimensional pinning regime.