engleski

Specific heat of the Yb(0.5)Y(0.5)InCu(4)

We report measurements and data analysis of the specific heat of Yb(0.5)Y(0.5)InCu(4). The measurements were performed in the temperature range between 2 K and 300 K and in magnetic field of 0 T and 5 T. The specific heat data of the high-temperature local-moment (LM) phase of YbInCu(4) and of Yb(0.5)Y(0.5)InCu(4) for which the valence transition disappears, reflect the same underlying physics. The Y-dilution removes the valence phase transition in YbInCu(4), but keeps the essential characteristics of LM phase unchanged. This makes possible a study of LM phase at low temperatures, where the crystal field and the Kondo effects are more pronounced. The magnetic contribution to the specific heat at low temperature is significant. We attribute it to the magnetic response of Yb3+ ion and compare it with the calculated one for the single Yb3+ ion in a crystal field. We assume the gamma (8) quartet ground state and the two close-lying excited doublets gamma (7) and gamma (6). The upturn in magnetic specific heat, obtained at low temperatures, cannot be explained within this crystal field scheme. It can be attributed to the appearance of a week Kondo effect.

Heavy fermions; Valence fluctuations; Crystalline electrical field

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