Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 17: Heavy Fermions

TT 17.12: Vortrag

Mittwoch, 28. März 2007, 17:00–17:15, H18

Paramagnetic moment in RFe₂Ge₂ (R = Lu and Yb) — •Julia Ferstl, Helge Rosner, and Christoph Geibel — Max Planck Institut für Chemische Physik fester Stoffe

We synthesised polycrystals and then grew single crystals of YbFe₂Ge₂ and LuFe₂Ge₂. The analysis of their physical properties revealed the presence of a paramagnetic Fe-moment of   3 µ_B/Fe at high temperatures in both compounds, which strongly contrasts the well established non-magnetic behavior of Co and Fe in the RCo₂Si₂, RCo₂Ge₂ and RFe₂Si₂ compound series. Additionally a phase transition at T₀ ≈ 9 K appears in LuFe₂Ge₂, which likely corresponds to antiferromagnetic ordering of the Fe-moments. The observation of a paramagnetic Fe-moment is discussed in the context of results from LDA-calculations. Our results in YbFe₂Ge₂ further indicate an intermediate valent Yb state with a comparatively low characteristic 4f energy of   80 K. This corresponds to a valence close to but less then 3. At low temperatures we observe a heavy Fermion behaviour with a moderately enhanced Sommerfeld coefficient γ = 200 mJ·mol⁻¹K⁻².