The valence phase transition in solid solutions Yb1-xLaxInCu4 and Yb1-xCexInCu4

Full text: At TV ∼ 40 K, an intermetallic compound YbInCu4 experiences isostructural phase transition associated with change in the valence state of ytterbium ions. The study of specific heat C in the range 0.4 - 300 K at partial substitution of Yb for La and Ce had revealed qualitatively different trends in evolution of this phase transition. In Yb1-xLaxInCu4 system (0 < x < 0.25) the anomaly in specific heat for any composition possesses features pertinent for the first order phase transition. Two energy scales for Kondo interaction can be distinguished in this case for low temperature and high temperature phases. In Yb1-yCeyInCu4 system (0 < y < 0.2) there is an evolution from the first order phase transition in parent compound to behavior characteristic for concentrated Kondo systems with unique energy scale. (authors)