Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons - Poster Session
TT 20.10: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
High-field ESR on the Kondo-system YbRh2Si2 — •Uwe Schaufuß1, V. Kataev1, B. Büchner1, J. Sichelschmidt2, C. Krellner2, C. Geibel2, and F. Steglich2 — 1Leibniz Institute for Solid State and Materials Research IFW Dresden — 2Max Planck Institute for Chemical Physics of Solids, Dresden
YbRh2Si2 is a Kondo–system with a Kondo temperature TK∼25 K [1] . It is located very close to a quantum critical point related to a very weak AFM order below TN=65 mK and a critical magnetic field of BC=0.06 T at ambient pressure. Surprisingly an ESR signal typical of a local Yb3+ spin has been observed below TK at fields B≤ 0.7 T [2] . The occurrence of the ESR signal is unexpected because at T≪ TK the Yb3+ moments should be screened. In order to obtain a deeper insight in this unusual behaviour we have performed ESR measurements on single crystals of YbRh2Si2 at much higher fields (5 to 7.5 T) at temperatures from 3 to 25 K, i.e. in the region where one expects a crossover from a Non–Fermi liquid(NFL) to a Fermi–liquid (FL) phase [3] . We observe a strongly anisotropic signal which can be assigned to Yb3+ moments. The signal exhibits a pronounced dependence on temperature and the magnetic field. We discuss the puzzling controversy between the observation of ESR which shows properties characteristic of a local Yb3+ moment and the Kondo state of YbRh2Si2.
1 O. Trovarelli et al.: Phys. Rev. Lett. 85, 626 (2000)
2 J. Sichelschmidt et al.: Phys. Rev. Lett. 91, 156 401 (2003)
3 K. Ishida et al.: Phys. Rev. Lett. 89, 107 202 (2002)