https://doi.org/10.1007/s100510170005
A systematic study of the role of Nd/Ba disorder on the superconducting properties of Nd1+xBa2-xCu3O7-8 thin films
1
INFM and Dipartimento di Scienze Fisiche, Università di Napoli Federico II,
80125 Napoli, Italy
2
Département de Physique de la Matière Condensée, Université de Genève,
1211 Genève 4, Switzerland
Corresponding author: a salluzzo@na.infn.it
Received:
11
May
2001
Published online: 15 November 2001
The role of Nd/Ba disorder on the superconducting properties of NdBa
Cu3O
epitaxial thin
films has been systematically studied. The temperature dependence of the ab-plane penetration
depth of highly c-axis epitaxial samples having different Nd/Ba composition has been measured by
an inverted microstrip resonator technique. Stoichiometric films (x=0) exhibit a linear penetration
depth at low temperature, while Nd-rich films (0< x< 0.3) show a T2 law. We find that for low Nd
excess it is possible to obtain a reasonable fit of the data in the full temperature range using the d-wave picture, with the assumption that Nd at Ba site plays the role of unitary scattering center. At
high concentration, the low temperature data can be instead explained supposing that excess Nd
acts as impurity with intermediate strength. The dependence of the critical temperature and of the
zero temperature superfluid density on disorder have been also studied. It is found that these two
quantities are correlated in a way analogous to what reported for YBCO films and single crystals
having Zn, Ni impurities at Cu site. An attempt to explain the results using a s-wave approach, as in the two-gap model, is able to reproduce the data but gives results quantitatively conflicting. On the contrary a self-consistent picture within a d-wave framework can be obtained taking into
account the effect of localization and suppression of the order parameter at impurity sites in the
case of both low and high impurity content.
PACS: 74.76.Bz – High-Tc films / 74.72.Jt – Other cuprates
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001