Absence of three-dimensional XY behavior in the magnetic penetration depthof YBa2Cu3O7-delta films

We have studied the transition region of numerous superconducting YBa2Cu3O7 -delta films through measurement of the magnetic penetration depth lambda(T ). Contrary to published results on YBa2Cu3O7-delta crystals, lambda(T) doe s not display three-dimensional XY behavior to within 0.5 K of T-c. Measure ments are performed in negligible external magnetic fields on films made by sputtering, coevaporation, and pulsed-laser deposition. For the samples wi th the narrowest transitions, as determined from the width of the peak in t he real conductivity sigma(1)(T), the superfluid density is mean-field-like to within 0.2 K of T-c. [S0163-1829(99)07109-X].