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Crystal field levels scheme for Yb(x)Y(1-x)InCu(4) obtained from susceptibility data

We report measurements and data analysis of the susceptibility of Yb(x)Y(1-x)InCu(4). We show that the susceptibility data of the high-temperature local-moment (LM) phase of YbInCu(4) and of Yb(x)Y(1-x)InCu(4)for x < 0.70, for which the valence transition disappears, reflect the same underlying physics. All the susceptibility data, for dierent x, can be scaled to the same curve down to 6 K, where some small differences between the susceptibilities appears. This curve coincide with magnetic response of the LM phase of the stoichiometric, x = 1, compound and we assume that the dilution removes the phase transition, but keeps the essential characteristics of LM phase unchanged. This makes possible a study of LM phase at low temperatures, where the crystal field effects are more pronounced and enables us to obtaine the crystal field levels scheme for Yb3+ ion in YbInCu(4). The data analysis suggests that the LM phase can be regarded as a static mixture of Yb3+ and Yb2+ ions, where the mixing ratio changes with doping. The absence of saturation effects at low temperatures suggests that the Kondo interaction is much weaker than it was reported previously. The crystal field calculations give the best fit for the quartet ground state, and the two excited doublets, which fits the susceptibility data excellently down to 10 K.

YbInCu4; crystal electric field; magnetic susceptibility; valence fluctuations

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