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TT: Tiefe Temperaturen

TT 16: Postersitzung II: Amorphe und Tunnelsysteme, Mesoskopische Systeme, Schwere Fermionen, Kernmagnetismus

TT 16.3: Poster

Tuesday, March 27, 2001, 14:30–17:00, Rang S\ 3

Temperature and intensity dependence of the acoustic properties in the normal and superconducting state of amorphous ZrCu — •R. König¹, I. Usherov-Marshak¹, M.A. Ramos², P. Esquinazi³, J. Arcas-Guijarro⁴, and A. Hernando-Mañeru⁴ — ¹Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth — ²Depart. de Física de la Materia Condensada C-III, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain — ³Abt. Supraleitung und Magnetismus, Universität Leipzig, D-04103 Leipzig — ⁴Instituto de Magnetismo Aplicado, Las Rozas, E-28230 Madrid, Spain

The study of the intensity dependence of the internal friction Q⁻¹ and of the relative change of sound velocity Δv/v of the amorphous metal PdSiCu [M. A. Ramos et al. Phys. Rev. B 61, 1059 (2000)] plays a particularly important role to confirm the temperature dependence of these properties in a wide range as predicted by the tunneling model in the zero strain limit. The question whether amorphous metals also reveal a universal behaviour in the limit of small acoustic intensities is currently investigated on two Zr_xCu_1−x samples with x=0.3 (superconducting transition at T_c=0.1 K) and x=0.4 (T_c=0.28 K) using the vibrating reed technique at temperatures 0.1 mK<T<1 K. The temperature dependence of Q⁻¹ and Δv/v in the normal and superconducting state at finite acoustic intensity is similar to that observed in former studies of ZrCu alloys with higher T_c. We discuss the influence of the acoustic intensity on the acoustic properties, and to which extend the conduction electrons affect the intensity dependence of Q⁻¹ and Δv/v.