SURFACE-ACOUSTIC-WAVE MEASUREMENTS OF YBA2CU3O7-DELTA THIN-FILMS AND SINGLE-CRYSTALS

Surface acoustic wave (SAW) velocity and attenuation measurements have been performed on high-temperature superconducting YBa2Cu3O7-delta (Y BCO) thin films (deposited on nonpiezoelectric substrates), and YBCO s ingle crystals, A ''bridge'' technique is employed in which piezoelect ric substrates, patterned with interdigital transducers, are bonded to the sample under investigation. The temperature dependence of 168 MHz SAW attenuation in a single crystal near its superconducting transiti on has been measured in applied magnetic fields up to 1.6 T. Features are seen above the superconducting transition temperature which may be indicative of a transition in the electric polarization of the materi al. A. field-dependent attenuation peak, seen in the superconducting s tate, is discussed in terms of the theory of thermally activated vorte x motion. (C) 1997 American Institute of Physics.