EXPERIMENTAL-STUDY OF THE DIMENSIONALITY IN BI2SR2CACU2O8- TEMPERATURE AND MAGNETIC-FIELD DEPENDENCE(X )

We present an experimental study of the dimensional crossover present in the extremely anisotropic superconductor Bi2Sr2CaCu2O8+x by means o f measurements of the onset field for the dissipation H as a function of the temperature and of the orientation theta between the field dir ection and the a, b plane. The crossover is experimentally shown to de pend on the strength of the applied magnetic field in a narrow tempera ture range below T(c). The entire set of experimental data is describe d by a coupled-layers model, in which a decoupling can be induced by a sufficiently high magnetic field. The anisotropy ratio is found to de pend strongly on the temperature and the model of coupled slabs of fin ite thickness quantitatively describes the data.