Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 6: Correlated Electrons: Heavy Fermions

TT 6.9: Talk

Monday, February 25, 2008, 11:45–12:00, EB 202

ESR Study on CeRuPO single crystals — •Tobias Förster, Jörg Sichelschmidt, Cornelius Krellner, and Christoph Geibel — Max Planck Institut f. Chemische Physik Fester Körper, Nöthnitzer Str. 40, 01187 Dresden, Germany

Until 2003 it was believed that the Electron Spin Resonance signal (ESR) from a Kondo ion in a dense Kondo system is not observable, because of the strong broadening due to 4f/5f- conduction electron hybridization. Hence the first observation of such a signal in YbRh₂Si₂ was a big surprise[1]. Very recently we found further Yb- and Ce-compounds that show well defined ESR signals [2].
In this contribution we will concentrate on single crystal data from the ferromagnetic Kondo-lattice system CeRuPO[3]. The recorded spectra show an asymmetry which is related to the local Ce³⁺ion (Γ₆ wave function) in tetragonal point symmetry. This is surprising because to the best of our knowledge an ESR signal due to dense Ce³⁺ magnetic moments in an environment with conduction electrons has only been reported for CeP. This unexpected result is neither specific to Ce-based compounds nor to compounds with Kondo-like properties nor to the proximity of a (quantum) critical point. It turns out that strong ferromagnetic correlations in the electronic system are essential for the ESR observability of concentrated magnetic ions in intermetallic systems.[2]

[1] J. Sichelschmidt et al., Phys. Rev. Lett. 91, 156401 (2003)

[2] C. Krellner et al., submitted to Phys. Rev. Lett.

[3] C. Krellner et al., Phys. Rev. B 76,104418 (2007)