Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 19: Correlated Electrons: Quantum-Critical Phenomena
TT 19.9: Talk
Tuesday, February 26, 2008, 16:15–16:30, H 3010
Thermal expansion and magnetostriction measurements on a CeCu5.85Au0.15 single crystal — •Stefanie Drobnik1,2, Kai Grube1, Roland Schäfer1, Frédéric Hardy1, Christoph Meingast1, Oliver Stockert3, and Hilbert von Löhneysen1,2 — 1Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe, Germany — 2Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe, Germany — 3MPI für chemische Physik fester Stoffe, 01187 Dresdenm, Germany
A well-studied magnetic quantum critical point (QCP) exists at the onset of antiferromagnetic order in the heavy-fermion system CeCu6−xAux with a critical gold concentration of xc≈0.1. Due to the instability at the QCP the entropy S shows at finite temperatures a maximum as a function of x, volume, or pressure p. The maximum leads to a sign change of the thermal expansion coefficient, α = −(1/V)(∂ S/∂ p), and of the Grüneisen parameter Γ, the ratio of α and specific heat. This feature and the divergence of Γ at T→0 are important thermodynamic probes to detect and classify QCPs. We report low-temperature thermal expansion and magnetostriction measurements on a CeCu5.85Au0.15 single crystal with a Néel temperature of TN ≈ 90 mK. The thermal expansion was measured along all orthorhombic axes in a temperature range of 30 mK < T < 10 K in magnetic fields parallel to the c axis of up to 3 T. The results are compared with theoretical predictions and measurements on other heavy-fermion compounds close to a QCP.