Eur. Phys. J. B 5, 159-162 (1998)
https://doi.org/10.1007/s100510050429

Penetration depth measurement in high quality YBa₂Cu₃O_7-x thin films

¹ School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Science, Tel Aviv University, Ramat Aviv 69978, Israel
² Department of Physical Electronics, Faculty of Engineering, Tel Aviv University, Ramat Aviv 69978, Israel
³ UMR CNRS/Thomson-CSF,91404 Orsay, France

Corresponding author: ^a farber@post.tau.ac.il

Received: 22 July 1997
Revised: 11 March 1998
Accepted: 23 June 1998
Published online: 15 September 1998

Abstract

The parallel plate resonator method has been used for measuring high quality YB_a2C_u3O₇-_x (YBCO) thin films, which have low temperature residual losses comparable to those previously obtained in single crystals. The surface resistance and the real part of the conductivity show a non-monotonic behaviour with a broad peak around 45 K. The penetration depth and the real part of the conductivity vary linearly at low temperatures. The lowest penetration depth linear fitting has a slope value of 2.2 Å/K to 2.5 Å/K up to 20 K which is lower than previous measurements on YBCO single crystals. An interpretation of this smaller slope in terms of the generally accepted d-wave order parameter symmetry presents difficulties.