Dresden 2003 – scientific programme
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TT: Tiefe Temperaturen
TT 14: Postersitzung III (Neue u. unkonventionelle Supraleiter, Anwendungen der Supraleitung, Dünne Schichten, JJs und SQUIDs, Schwere Fermionen, Kondo-Systeme)
TT 14.50: Poster
Wednesday, March 26, 2003, 14:30–19:00, P2c
Yb4Rh7Ge6: a system with a well localised trivalent Yb-state — •J. Ferstl and C. Geibel — Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
In an attempt to grow single crystals of YbRh2Ge2, the homologues of the quantum critical system YbRh2Si2, we obtained single crystals of Yb4Rh7Ge6. Since, to our knowledge, no information on the properties of this compounds have yet been reported, except for the lattice parameters, we started an investigation of its physical properties. We shall present preliminary results of resistivity, susceptibility and specific heat measurements. The measurements indicate a system with a well localized trivalent Yb-state. The susceptibility follows at high temperatures a Curie-Weiss law with a Curie-Weiss temperature of -25 K and an effective moment of µ eff = 4.5 µB, the expected value for a trivalent Yb-state. No evidence for Kondo effect is observed in the resistivity. The specific heat measurement shows a very sharp peak at 480mK, which indicates a magnetic phase transition. The value for the specific heat at this temperature is very high, C∣TN 12Jmol−1K−1 and corresponds to the expected Mean Field Value for a doublet crystal electric field (CEF) ground state. The presence of a doublet is supported by the temperature dependence of the entropy, which levels out above 2K at a value close to RLn2. Specific heat data at higher temperatures suggest a CEF-excited state at around 100K. The properties of Yb4Rh7Ge6 shall be discussed in comparison to related compounds.