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

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