Paramagnetic moment in RFe2Ge2 (R=Lu and Yb)

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 μB/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. (orig.)