Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.77: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

¹¹⁹Sn solid state NMR as a local probe for correlations in CeRu₄Sn₆ — •Eva Maria Brüning¹, Michael Baenitz¹, Andrei Gippius², André Strydom³, Silke Bühler-Paschen¹, and Frank Steglich¹ — ¹Max-Planck-Institute for Chemical Physics of Solids, Dresden, Germany — ²Moscow State University, Faculty of Physics, Moscow, Russia — ³Department of Physics APK, University of Johannesburg, South Africa

A ¹¹⁹Sn NMR study on the tetragonal semimetal CeRu₄Sn₆ and the metallic structural homologue LaRu₄Sn₆ is presented. At low fields (1.8 T, 28.5 MHz) a broad NMR line with small (-0.33%) and nearly independent negative Knight shift K(T) is observed, whereas at larger fields (up to 7.5 T) a structure in the spectra could be resolved. The NMR spectra are well represented by a superposition of two broadened anisotropic S=1/2 lines, consistent with the two different Sn sites in the tetragonal structure. The behavior of the spin-lattice relaxation rate 1/T₁ at 28.5 MHz above approximately T = 20 K is consistent with a narrow-gap semiconductor (1/T₁ ∼ Texp(−Δ/k_BT), Δ/k_B = 33 K). The formation of correlations become apparent below T^* = 10 K where an upturn is observed in 1/T₁T. This is consistent with the specific heat results in the framework of the Korringa model where (T₁T)⁻¹ ∝ K² ∝ N_EF² ∝ (C/T)² is valid. 1/T₁ investigations at higher fields show the supression of the low-temperature upturn. In conclusion the results for CeRu₄Sn₆ suggest the formation of a ground state of strongly correlated quasiparticles within a low-carrier density.