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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.12: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

DC-Susceptibility of CeCu_6−xAu_x at very low temperatures — •Andreas Hamann¹, Tihomir Tomanic¹, Hilbert v. Löhneysen^1,2, and Oliver Stockert³ — ¹Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — ²Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe — ³MPI für chemische Physik fester Stoffe, 01187 Dresden

CeCu₆ is a prototype heavy-fermion system that is rather well described by Fermi liquid (FL) theory. Au doping introduces long-range incommensurate antiferromagnetism for x > x_c ≈ 0.1. In the vicinity of the quantum critical point x_c significant deviations from FL theory have been observed in measurements of the specific heat, magnetic susceptibility and the electrical resistivity. In addition, highly unusual features were observed in inelastic neutron scattering [1,2]. In particular, the energy integrated dynamical as well as the statical susceptibility could be described by χ⁻¹ ∝ (θ(q))^α + c T^α with α = 0.75 [1]. We report measurements of the low-field dc-susceptibility χ(T) of CeCu_5.9Au_0.1 and CeCu_5.85Au_0.15 down to temperatures around 40 mK. Our data for x=0.1 show for T 200 mK deviations from the above χ⁻¹ expression signaling a crossover for a smaller exponent α than previously found for higher T and B. For x=0.15 we see clear experimental evidence for the sharp onset of antiferromagnetic order below T_N ≈ 82 mK for x = 0.15. We compare our data in detail with the previous work [1].

[1] A. Schröder et al., Nature 407, 6802 (2000)

[2] O. Stockert et al., Phys. Rev. Lett. 80, 5627 (1998)