3D-2D dimensional crossover in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ films

We show that, in fully oxidized ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ c-axis oriented films, the changes induced in the angular and field dependence of the magnetoresistivity ${\mathrm{\rho }}_{\mathit{a}\mathit{b}}$ by increasing the temperature towards ${\mathit{T}}_{\mathit{c}}$ are similar to those caused by a lowering in oxygen content. This remarkable behavior can be interpreted as due to a crossover from a three-dimensional to a two-dimensional system as T approaches ${\mathit{T}}_{\mathit{c}}$. Moreover, our critical current data mimic the behavior observed by Qi Li et al. in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$/(${\mathrm{Pr}}_{\mathit{x}}$ ${\mathrm{Y}}_{1\mathrm{-}\mathit{x}}$)${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ multilayers, suggesting the possibility that chain planes are superconducting.