Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 20: Poster:Schichten(1-29),Spintrsp(30-45),Ex-Bias(46-63),Spindyn(64-75),Mikromat.(76-80),Cluster(81-94),Abbv.(95-99),Obflm(100-02),SpElek.(103-09),E-Theo(110-14),Mikromag.(115-16),Spin+PÜ(117-26),Mag.Mat.(127-51),Meth.(152-55),Mol.Mag(156-59),Kondo(160-65
MA 20.163: Poster
Montag, 7. März 2005, 14:00–18:00, Poster TU C
YbFe4Sb12: Divalent Ytterbium State and Itinerant Magnetism of the Skutterudite Host Structure — •W. Schnelle, A. Leithe-Jasper, H. Rosner, M. Schmidt, M. Baenitz, J.A. Mydosh, and Y. Grin — Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany
The filled skutterudite YbFe4Sb12 has been investigated by Maple et al. [1] and other groups [2] and its remarkable properties have been interpreted involving an intermediate valence state of Yb and heavy-fermion behaviour at low temperatures. The large linear term γ in the specific heat (≈ 140 mJ/mol K2) and the ‘S’-shape of the metallic resistivity have been presented as evidence for a Kondo effect and heavy electrons. However, the filled skutterudites MFe4Sb12 with M = Na, K, Ca, Ba [3] and La all display γ terms of 100–200 mJ/mol K2 and strongly curved resistivities ρ(T), irrespective of their magnetic ground state. Also, their paramagnetic effective moments are quite similar and derive almost completly from the itinerant magnetism of the Fe4Sb12 host which is only slightly modified by the various filler atoms. Conclusively, X-ray absorption spectra (XANES) at the Yb LIII treshold demonstrate that Yb is in a divalent 4f14 state and thus YbFe4Sb12 can neither exhibit a Kondo effect nor show conventional heavy fermion behaviour.
[1] N.R.Dilley et al. Phys. Rev. B 58, 6287 (1998). S.V.Dordevic et al. Phys. Rev. Lett. 86, 684 (2001).
[2] see e.g. E.Bauer et al. Acta Phys. Polon. B 34, 595 (2003).
[3] A. Leithe-Jasper et al. Phys. Rev. B, in print (1 Dec 2004).