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TT: Fachverband Tiefe Temperaturen

TT 44: Poster Session Correlated Electrons

TT 44.79: Poster

Donnerstag, 17. März 2011, 10:00–13:00, P1

Low temperature spin excitation spectrum of FeSi by polarized neutron spectroscopy — •Sven Krannich¹, Yvan Sidis², Jean-Michel Mignot², Daniel Lamago^1,2, Frank Weber¹, Alexander Ivanov³, and Paul Steffens³ — ¹Karlsruhe Institute of Technology, Institute of Solid State Physics, 76021 Karlsruhe, Germany — ²Laboratoire Léon Brillouin, CEA-Saclay, F-91191 Gif sur Yvette Cedex, France — ³Institute Laue Langevin, 156X, 38042 Grenoble Cedex 9, France

We investigated the spin excitation spectrum of FeSi using the thermal triple axis neutron spectrometer IN20 at the Institute Laue Langevin, Grenoble, with polarization analysis. FeSi displays a behavior which has, so far, only been observed in f-electron containing Kondo insulators. Therefore, it has often been claimed to be the first 3d system belonging to this class of materials [1]. A temperature dependent energy gap was observed in optical spectroscopy [2], but measurements of inelastic magnetic scattering via neutrons have been restricted to T ≥ 150 K so far [3] and did not report gap signatures. We measured magnetic scattering between room temperature and T = 15 K over a large energy range up to energies of 80 meV. Particular attention was devoted to possible spin-exciton formation at energy transfers below the gap value at low temperatures as observed in the Kondo-insulator YbB₁₂ [4].
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