On the role of Nd/Ba disorder on the superconducting properties of Re1(NdxBa2-x)Cu3O7-delta (Re= Nd, Y) thin films

The role of disorder on the superconducting properties of Re-1(NdxBa2-x)Cu3O7-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 characterised by different x (0, 0.08, and 0.12). In situ X-ray Photoemission Spectroscopy (XPS), Scanning Tunneling Microscopy (STM), and nonconventional x-ray diffraction measurements have been used to determine the exact composition and the structural properties of each sample. The temperature dependence of the ab-plane penetration depth of highly c-axis epitaxial samples, characterised by different Nd/Ba ratios, has been determined by an inverted microstrip resonator technique. Results on the Nd1-xBa2-xCu3O7-delta system show that only stoichiometric films exhibit a linear penetration depth at low temperature while Nd-rich films show a T-2 law. Preliminary measurements on the Y-1(NdxBa2-x)Cu3O7-delta system confirm these results. The data are analysed in the framework of the d-wave model taking into account the effect of impurities on the superconducting properties.