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TT: Tiefe Temperaturen

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

TT 16.4: Poster

Dienstag, 27. März 2001, 14:30–17:00, Rang S\ 3

Acoustic properties of compacted metal powders at low temperatures — •Igor Usherov-Marshak and Reinhard König — Physikalisches Institut, Universität Bayreuth, D-95440 Bayreuth

Using the vibrating reed technique we have investigated the acoustic properties, i.e. the internal friction and the relative change of sound velocity, of high purity compacted silver (grain sizes 0.1 µm and 2 µm, packing fraction f = 0.6) and platinum powders (grain size 2 µm, f = 0.6) as well as of high purity Ag and Pt foils (thickness 100 µm) at frequencies of about 1 kHz in the temperature range between 0.1 mK and 500 mK. All samples investigated so far show a maximum in the change of sound velocity at a temperature T_co and logarithmic temperature dependences above and below it. We observe significantly different slopes of the temperature dependence of the sound velocity for the foils and the powder compacts below and comparable slopes above Tco. The internal friction appears to be temperature dependent over the whole temperature range investigated. We discuss the dependence of the acoustic properties of the powder compacts on temperature and acoustic intensity in comparison with results previously obtained on polycrystalline as well as on amorphous metals.