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Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 43: Correlated Electrons: Heavy Fermions 2

TT 43.6: Talk

Thursday, March 26, 2009, 17:00–17:15, HSZ 301

Exotic Ground State of CeRu4Sn6 Investigated by Means of Specific-Heat and NMR — •Eva Maria Brüning1, Manuel Brando1, Michael Baenitz1, André Strydom2, Russel E. Walstedt3, and Frank Steglich11Max-Planck-Institut für Chemische Physik Fester Stoffe, Dresden, Germany — 2Physics Department, University of Johannesburg, South Africa — 3Physics Department, University of Michigan, MI, USA

The tetragonal compound CeRu4Sn6 is a narrow-gap semi-metal and shows no phase transition down to 50 mK. We performed field-sweep 119Sn NMR measurements at different frequencies (47, 70, 100 and 119 MHz) down to 2 K as well as specific-heat measurements in magnetic fields up to 10 T and temperatures down to 65 mK. The spin-lattice-relaxation rate 1/T1 in the high-T range (300 K to 20 K) is field independent and could be consistently fitted with a model for a narrow gap semi-metal (1/T1Texp(−Δ /kBT)) with a gap of Δ/kB ≃ 30 K. This confirms the results from resistivity and thermopower measurements. Below 10 K, 1/T1 becomes strongly field dependent, whereas higher fields lead to a stronger reduction of 1/T1. The low-T range could be fitted with an activated behavior (1/T1 ∝ exp(−Δ/kBT)), where Δ/kB increases with increasing field. This scenario is strongly supported by specific-heat investigations. Both results can be described consistently by assuming a double Cauchy-Lorentz function for the residual in-gap density of states N(E). The ground state is governed by these correlated states which show Zeeman-type splitting in magnetic fields.

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