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TT: Fachverband Tiefe Temperaturen

TT 53: Correlated Electrons: Heavy Fermions

TT 53.8: Vortrag

Donnerstag, 14. März 2013, 11:30–11:45, H19

Eu valence and Fermi-surface development in EuX₂Si₂ (X = Co, Rh, Ir) systems — •K. Götze^1,5, S. Seiro², C. Geibel², H. Rosner², V. Petzold², A. Polyakov¹, J. Wosnitza¹, I. Sheikin³, and A. Suslov⁴ — ¹Hochfeld-Magnetlabor Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany — ²MPI for Chemical Physics of Solids, Germany — ³LNCMI-Grenoble, France — ⁴National High Magnetic Field Laboratory, Tallahassee, USA — ⁵TU Dresden, Institut für Festkörperphysik, Germany

The valence-fluctuating Eu systems EuX₂Si₂, with X being the transition metal Co, Ir, or Rh, show different types of ground states, strongly depending on X. The instability of the Eu 4f shell underlies this phenomenon and leads among other effects to different valence states ranging from Eu²⁺ over mixed valence and intermediate valence behavior to Eu³⁺ [1]. Investigations on the structure and the magnetic behavior of EuCo₂Si₂, EuIr₂Si₂, and EuRh₂Si₂ have revealed their Eu valence. Further experiments on specific heat and resistivity gave insights to magnetic ordering, electronic correlations, and possible valence fluctuations. We report about a systematic de Haas-van Alphen study on the Fermi-surface development of the EuX₂Si₂ compounds in magnetic fields up to 35 T. High-quality single crystals were available for the first time. We will focus on the Fermi-surface topology obtained by angle dependent measurements and discuss a comparison to band-structure calculations.

This work was partly supported by EuroMagNET, EU contract 228043 and DFG within GRK1621.
[1] Z. Hossain et al., Journal of Alloys and Compounds 323-324 (2001).