Regensburg 2007 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 20: Correlated Electrons - Poster Session
TT 20.2: Poster
Mittwoch, 28. März 2007, 14:00–17:45, Poster A
Spin Dynamics of EuCu2(Ge(1−x)Six)2 probed by Electron Spin Resonance — •Tobias Foerster1, Joerg Sichelschmidt1, Zakir Hossain2, and Christoph Geibel1 — 1Max Planck Institut f. Chemische Physik Fester Körper, Nöthnitzer Str. 40, 01187 Dresden, Germany — 2Department of Physics, Indian Institut of Technology, Kanpur, India
The intermetallic alloy EuCu2(Ge(1−x)Six)2 can be used to investigate the transition from divalent antiferromagnetic state to the valence fluctuating state of Eu. By tuning x one observes an antiferromagnetic ordered state which is stable up to xc ≈ 0.65. For x > 0.5 the system shows valence fluctuation behaviour. Additionally, for x > 0.4 Kondo-like behaviour appears, becoming pronounced around xc where also heavy Fermi liquid formation is observed.
We investigated polycrystalline samples of EuCu2(Ge(1−x)Six)2 (0≤ x≤1) by Electron Spin Resonance (ESR) at X-Band frequencies. All compositions show well defined ESR spectra at a g-factor typical for Eu2+ ions. We observe different temperature dependencies of the line width in different regions of the phase diagram.
For example the sample with x=0.6375 shows a line width increase for rising temperature with a change of slope near the estimated Kondo temperature, TK ≈ 30K. This behaviour is very similar to the pattern observed for ESR probe spins embedded in a Kondo lattice system. The ESR spectra are analyzed concerning the backround of bulk measurements.