Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 43: Correlated Electrons: Heavy Fermions 2

TT 43.5: Talk

Thursday, March 26, 2009, 16:45–17:00, HSZ 301

Electronic Correlations and Non-Fermi-Liquid Behaviour in ACu₃Ru₄O₁₂–Perovskites — •Axel Günther¹, Alexander Krimmel¹, Alois Loidl¹, Wolfgang Krätschmer¹, Heiko Dekinger¹, Norbert Büttgen¹, Ernst-Wilhelm Scheidt², Denis Sheptyakov³, and Hannu Mutka⁴ — ¹Experimentalphysik 5, Zentrum für elektronische Korrelationen und Magnetismus, Universität Augsburg, 86135 Augsburg, Deutschland — ²CPM, Institut für Physik, Universität Augsburg, 86135 Augsburg, Deutschland — ³Labor für Neutronenstreuung, ETHZ & PSI, 5232 Villigen PSI, Schweiz — ⁴Institut Laue Langevin, 38042 Grenoble Cedex 9, France

Among the large variety of AC₃B₄O₁₂–type perovskites, the copper–ruthenates (C=Cu, B=Ru) form a subclass exhibiting strongly correlated electron behaviour. A special feature of these compounds is that the ideal stoichiometry and structure is preserved for a large number of different A–site cations with different valence states. We have systematically studied the electronic properties by specific heat, magnetic susceptibility, transport, NMR/NQR and neutron scattering experiments. The compound A=Ca is a correlated metal showing non–Fermi–liquid behaviour below 2K, as indicated by a logarithmic increase of the specific heat and deviations from a Korringa behaviour of the spin lattice relaxation rate. In the case of A=Pr, an anomaly in the specific heat occurs at 0.5K whose maximum shifts to higher temperatures with increasing magnetic field. Along with data acquired from inelastic neutron scattering we obtain strong indications for a pronounced crystal field splitting.