Order-disorder transition and the zero-dimensional vortex pinning regime inBi2Sr2CaCu2O8+δ

Abstract

We make a comparative study between the $\mathrm{ab}$ plane's dc critical current and the ac transverse magnetic permeability ${\ensuremath{\mu}}_{\ensuremath{\perp}}$ in the Campbell limit for optimally doped and overdoped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ 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.