Dimensional crossover of vortex fluctuations in Bi₂Sr₂CaCu₂O₈

Abstract

We have measured the temperature and magnetic field dependences of the magnetization for a single crystal Bi₂Sr₂CaCu₂O₈ and have observed changes in the magnetization which are described to changes in the coupling strength between Josephson coupled superconducting layers. From those experiments we have obtained the temperature dependence of the irreversible field in the 3D state and a weakly coupled 2D state. A dimensional crossover field H_2D(T) has been also obtained from a magnetic field dependence of magnetization. We propose a new magnetic phase diagram illustrating the various transformations that occur in the electromagnetic response of this layered superconductor.