Accession Number : ADA307816

Title :   Ultrasonic Characterization of High Tc and Other Unconventional Superconductors.

Descriptive Note : Summary rept. 1 Jun 95-31 May 96,

Corporate Author : WISCONSIN UNIV-MILWAUKEE DEPT OF PHYSICS

Personal Author(s) : Levy, Moises

PDF Url : ADA307816

Report Date : MAY 1996

Pagination or Media Count : 9

Abstract : Ultrasonic techniques have been used to characterize the properties of high Tc superconductors. A model is being developed to explain the radiation losses from a resonating fused silica sample. A new very sensitive resonant technique was developed for studying vortex motion in the superconducting state of an untwinned single crystal of YBCO. Evidence is obtained for a transition from a soft vortex system to a rigid strongly interacting vortex system in the vicinity of the superconducting transition temperature. A percolation model developed in our group to describe surface acoustic wave attenuation in a granular superconducting film was modified to include the resistivity of the individual grains in a matrix of Josephson junctions. SAW measurements using a pontoon technique on both a single crystal and a thin film of YBCO demonstrate the importance of pinning sites in determining the nature of a vortex transition; the vortex system will undergo a depinning transition if the pinning density is large and a melting transition if it is small. Resonant ultrasonic spectroscopy data obtained as a function of gas pressure has been analyzed.

Descriptors :   *VORTICES, *TRANSITION TEMPERATURE, *HIGH TEMPERATURE SUPERCONDUCTORS, *SURFACE ACOUSTIC WAVES, SINGLE CRYSTALS, FUSED SILICA, ULTRASONICS, RESONANCE, ACOUSTIC MEASUREMENT, LOSSES, ELECTRICAL RESISTANCE, RESONATORS, ACOUSTIC ATTENUATION, COPPER OXIDES, PERCOLATION.

Subject Categories : Electricity and Magnetism
      Line, Surface and Bulk Acoustic Wave Devices

Distribution Statement : APPROVED FOR PUBLIC RELEASE