Dresden 2009 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 43: Correlated Electrons: Heavy Fermions 2
TT 43.11: Vortrag
Donnerstag, 26. März 2009, 18:30–18:45, HSZ 301
X-ray Absorption Spectroscopy of the Narrow Gap Semiconductor FeSb2 — •N. Hollmann1, Z. Hu1, C. Chang1, J. Gegner1, S. Johnsen2, B.B. Iversen2, J.C. Cezar3, N. Brookes3, H.H. Hsieh4, H.-J. Lin4, C.T. Chen4, P. Sun5, N. Oeschler5, F. Steglich5, and L.H. Tjeng1 — 1II.Physikalisches Institut, University of Cologne — 2Department of Chemistry, University of Aarhus, Denmark — 3ESRF, Grenoble, France — 4NSRRC, Hsinchu, Taiwan — 5MPI for Chemical Physics of Solids, Dresden
FeSb2 recently attracted much attention due to the observation of extremely large values of the Seebeck coefficient S∼−45000µVK−1 at 10K and the thermoelectric power S2ρ−1=2300µWK−2cm−1 at 12K, the latter being a record high [1]. The material is being discussed in the framework of a Kondo insulator model with similarities to FeSi. FeSb2 exhibits a diamagnetic to paramagnetic crossover at ≈ 100K. The ground state was proposed to have the non-magnetic d4 configuration. Contrary to that, band structure calculations predict a d6 configuration for the Fe. If true, this could suggest a different scenario with similarities to that of LaCoO3 [2]. By now, no experimental data exists to prove the valency of the Fe ion. We have performed X-ray absorption spectroscopy on FeSb2, as it is an ideal technique to study the valence and the spin state. The spectra directly show the valency for the Fe. Temperature-dependent linear dichroism and magnetic circular dichroism data will be discussed in the talk.
[1] A. Bentien et al., Europhys. Lett. 80, 17008 (2007).
[2] M.W. Haverkort et al., Phys. Rev. Lett. 97, 176405 (1996).