Evolution from heavy-fermion to mixed-valence behavior in the series CePt1-xIrxSi2

To study the evolution from heavy-fermion (HF) to mixed-valence (MV) behavi or upon substituting Pt for Ir in the ternary intermetallic compound CePtSi 2 we carried out X-ray diffraction, dc electric resistivity, Cc L-III-edge X-ray absorption spectra (XAS), dc susceptibility and specific heat measure ments in the series CePt1-xIrxSi2 (x = 0, 0.2,0.4,0.6,0.8, 1.0). The result s obtained suggest that the evolution from HF to MV behavior is likely due to the enhancement of hybridization between the Ce 4f-electron wave functio n and sp wave function of the adjacent transition metal ion. Besides, it wa s found that x similar to 0.6 is the borderline region between HF and MV re gimes. (C) 2001 Published by Elsevier Science Ltd.