Electronic states of CeT2X20 (T:transition metal, X=Zn and Cd).

The electronic state of single crystals of CeIr₂(Zn_1−xCd_x)₂₀ and CePt₂Cd₂₀ has been studied by measuring the electrical resistivity ρ and specific heat C. We found that by substituting Zn with Cd, the lattice parameter expands, and the electronic specific heat coefficient γ and A coefficient, which is T²-term in ρ, are enhanced. Our experimental results reveal that the electronic state of the intermediate valence compound CeIr₂Zn₂₀ changes to a moderately heavy fermion state due to the negative chemical pressure. On the other hand, C and ρ of CePt₂Cd₂₀ show a clear jump and an abrupt change of slope below 0.3 K, respectively, due to a magnetic transition. The relation between the hybridization strength and Ce valence state has also been investigated by X-ray absorption experiment. [ABSTRACT FROM AUTHOR]