Münster 1999 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 13: Amorphe Systeme

TT 13.3: Vortrag

Mittwoch, 24. März 1999, 16:00–16:15, F2

Temperature and intensity dependence of the acoustic properties of PdSiCu — •R. König¹, M. Ramos², P. Esquinazi³, and E. Gaganidze³ — ¹Experimentalphysik V, UniversitÄt Bayreuth, D-95440 Bayreuth — ²Departamento de Fisica de la Materia Condensada C-III, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid — ³Abt. Supraleitung und Magnetism, Universität Leipzig, 04103 Leipzig

We have performed a detailed studied of the acoustic properties of PdSiCu in the temperature range 0.2 mK < T < 500 mK and at a frequency of 489 Hz. The measurements have been performed using the vibrating reed technique, with the experimental cell attached to the flange of a Cu nuclear demagnetization refrigerator. Sound velocity variation shows a logarithmic dependence on temperature as well as an increase with acoustic intensity in agreement with earlier measurements. Strikingly, the internal friction shows also a logarithmic increase with temperature up to ∼ 20 mK. This result as well as the acoustic dependence at constant T reveal several puzzling features and clearly deviate from the simple behavior predicted in the kHz range by the tunneling model. Several possible explanations for these experimental features are discussed.