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TT: Tiefe Temperaturen
TT 19: Postersitzung III: Josephsonkontakte(1-25), SQUIDs, Sensoren, Detektoren(26-37), Supraleitung in Hochfrequenz und Elektronik(38-45), Präparation und Dotierung von HTSL(46-53), NMR und Ultraschall in HTSL(54-60), Thermodynamik, Magnetismus(61-68), Transporteigenschaften von HTSL(69-73), Spektroskopie, Ramanstreuung, param. Meissner-Effekt in HTSL(74-84), n-dotierte HTSL(85-91)
TT 19.58: Poster
Thursday, March 20, 1997, 15:30–19:00, Z1
Ultrasonic investigations of YBa2Cu3O7 thin films — •M. Stenger1, C. Barre1, J.-Y. Prieur1, J. Joffrin1, and J.-P. Contour2 — 1Lab. de Phys. des Solides, Univ. Paris Sud, Bât. 510, F-91405 Orsay — 2CNRS, UMR137 / Thomson-CSF/LCR, F-91404 Orsay
Important experiments which proved the validity of the BCS-theory for the classical superconductors were measurements of the absorption of ultrasound, which yield the temperature dependence of the superconducting gap function. For the new High-Tc materials, however, the lack of bulk mono-crystalline samples of sufficient size renders ultrasonic investigation complicated. On the other hand, good quality thin films are available, making ultrasonic measurements by surface acoustic waves possible. The disadvantage of using surface acoustic waves for this kind of experiments is the loss of sensitivity to changes in the elastic properties of the film material compared to bulk waves, due to the fact that a surface wave probes mostly the substrate material. We present an experimental setup to enhance the sensitivity of surface acoustic waves and show first results of measurements on YBa2Cu3O7 thin films on Lithiumniobate substrates in magnetic fields up to 3.5 T. An attenuation decrease in the superconducting regime, appearing at the critical temperature, is observed. However, for a detailed analysis, an increase in sensitivity would be necessary. We discuss further possible improvements of the setup.