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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.20: Poster

Mittwoch, 24. März 2010, 14:00–18:00, Poster D1

Equivalence of pressure and concentration tuning in CeCu_6−xAu_x — •O. Stockert¹, A. Hamann², V. Fritsch², A. Schneidewind³, and H. v. Löhneysen² — ¹Max-Planck-Institut CPfS, Dresden, Germany — ²Karlsruhe Institute of Technology, Karlsruhe, Germany — ³Joint Research Group Helmholtz-Zentrum Berlin - Technische Universität Dresden, FRM-II, Garching, Germany

In the prototypical heavy-fermion system CeCu_6−xAu_x two different quantum critical scenarios are discussed: the conventional spin-density-wave (SDW) scenario introduced by Hertz, Millis and Moriya and the local scenario by Schröder, Coleman, Si. While concentration and pressure tuning the quantum phase transition (QPT) are described by the local critical scenario, magnetic field tuning the QPT results in the conventional SDW scenario. In order to study how far the analogy between Au substitution and hydrostatic pressure holds, we performed elastic neutron scattering experiments on single crystalline CeCu_5.5Au_0.5 and investigated the magnetic structure under hydrostatic pressure. At a pressure of p = 8 kbar the Néel temperature and the propagation vector of the magnetic structure attain almost the values of CeCu_5.7Au_0.3. This concentration-pressure analogy away from the QPT is highly remarkable, since the ambient-pressure magnetic structures of CeCu_5.5Au_0.5 and CeCu_5.7Au_0.3 are quite different. The change of the magnetic structure of CeCu_5.5Au_0.5 under pressure appears to be of first order and to be determined by slight changes in the nesting properties of the Fermi surface. We will discuss our findings in comparison to the different QPTs in the system CeCu_6−xAu_x.