3D-2D DIMENSIONAL CROSSOVER IN YBA2CU3O7 FILMS

We show that, in fully oxidized YBa2Cu3O7 c-axis oriented films, the c hanges induced in the angular and field dependence of the magnetoresis tivity rho(ab) by increasing the temperature towards T(c) are similar to those caused by a lowering in oxygen content. This remarkable behav ior can be interpreted as due to a crossover from a three-dimensional to a two-dimensional system as T approaches T(c). Moreover, our critic al current data mimic the behavior observed by Qi Li et al. in YBa2Cu3 O7/(PrxY1-x)Ba2Cu3O7 multilayers, suggesting the possibility that chai n planes are superconducting.