Raman spectroscopy on nonstoichiometric Gd123 thin films

We performed the Raman measurements to investigate the effect of cation nonstoichiometry on Gd123 thin films. The Gd123 thin films are grown by a conventional pulsed laser deposition (PLD) method with cation off-stoichiometric target samples. The films show different superconducting (SC) properties (T-c, J(c)) from one another. The Ba-poor composition shows the best SC properties, while the Ba-rich composition shows the worst properties. The Raman spectra also depend on the compositions. All the spectra exhibit the five phonon peaks peculiar to 123-structure, however, some show also other peaks which result from oxygen deficiency in the chain structure, or also other origins. We discuss that the SC properties are strongly affected by the disorders of Ba and chain sites due to the cation nonstoichiometry through the Raman spectra. (C) 2007 Elsevier B.V. All rights reserved.