On the role of Nd/Ba disorder on the superconducting properties of Re-1(NdxBa2-x)Cu3O7-delta (Re= Nd, Y) thin films

The role of disorder on the superconducting properties of Re-1(NdxBa2-x)Cu3 O7-delta (Re = Nd, Y) epitaxial thin films has been studied. The films are deposited by Ar+O-2 magnetron and diode de sputtering from targets characte rised by different x (0, 0.08, and 0.12). In situ X-ray Photoemission Spect roscopy (XPS), Scanning Tunneling Microscopy (STM), and nonconventional x-r ay diffraction measurements have been used to determine the exact compositi on and the structural properties of each sample. The temperature dependence of the ab-plane penetration depth of highly c-axis epitaxial samples, char acterised by different Nd/Ba ratios, has been determined by an inverted mic rostrip resonator technique. Results on the Nd1-xBa2-xCu3O7-delta system sh ow that only stoichiometric films exhibit a linear penetration depth at low temperature while Nd-rich films show a T-2 law. Preliminary measurements o n the Y-1(NdxBa2-x)Cu3O7-delta system confirm these results. The data are a nalysed in the framework of the d-wave model taking into account the effect of impurities on the superconducting properties.