MAGNETIC-FIELD EFFECTS ON THE DIMENSIONAL CROSSOVER IN BI2SR2CACU2O8

The temperature-induced dimensional crossover present in the highly-an isotropic superconductor Bi2Sr2CaCu2O8 is experimentally shown to be a ffected by the external magnetic field. By studying the onset field fo r the resistivity H as a function of the angle v between the (a,b) pl ane and the direction of the magnetic field, it is found that at low t emperature the behavior is 2D, while it becomes 3D near T(c). In an in termediate range of temperature the dimensionality is magnetic-field d ependent. The results are in good agreement with theoretical models th at describe this superconductor as composed of a stack of superconduct ing slabs coupled via Josephson effect.