Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 39: Correlated Electrons: Heavy Fermions 1
TT 39.8: Vortrag
Donnerstag, 26. März 2009, 11:45–12:00, HSZ 304
Investigation of Yb2Pt6AL15 single crystals: heavy fermion system with a large local moment degeneracy — •Micha Deppe, Stefanie Hartmann, Monica E. Macovei, Niels Oeschler, Michael Nicklas, and Christoph Geibel — Max-Planck-Institute for Chemical Physics of Solids, 01187 Dresden, Germany
Possible new Cerium or Ytterbium based heavy fermion compounds for the study of a quantum critical point (QCP) are of high interest.
We studied Yb2Pt6AL15 because it exhibits an interesting quasi 2D crystal structure.
It crystallizes in the hexagonal structure type Sc1.2Fe4Si9.8 and
this structure presents RE2Al3 - layers separated by two Pt-Al layers in a large distance c/2 = 8.18 Å
between the RE2Al3 - layers and a large c/a ≈ 4 ratio.
Here we present our investigations of the magnetic properties by means of susceptibility χ(T), specific heat C(T), resistivity ρ(T) and thermoelectric power S(T)
measurements. While all properties follow in general the behavior typical for Kondo-lattice systems, χ(T) and Cp(T)/T
present broad maxima in the T range 17-35 K, which matches nicely the prediction of the Coqblin-Schrieffer model for
J = 7/2. A large degeneracy of the local moment is also supported by a reduced Kadowaki-Woods ratio. Thus, the analysis of all
investigated properties evidences Yb2Pt6Al15 to be a paramagnetic Kondo-lattice system with the whole J = 7/2 multiplet
involved in the formation of the Kondo state, a Kondo temperature of the order of 60 K, and a heavy Fermi-liquid ground state with
a Sommerfeld coefficient γ0 = 0.33 J/mol−Yb K−2 corresponding to a mass enhancement of the order of 30.