Abstract
At the transition temperature (Tv≈42 K) YbInCu4 with AuBe5-type structure exhibits a first-order isostructural valence transition from Yb3+ free ion state at high temperatures (HT) to the Fermi liquid state with an intermediate valence (Yb2.9+) at low temperatures (LT). In the LT phase a metamagnetic transition from the Fermi-liquid state to the Yb3+ state can also be induced by high magnetic field at Hv≈30 T. We will discuss the valence transition in the Yb1-xYxInCu4 system by measurements of susceptibility and high field magnetization in this paper. With increasing x, Tv and Hv decrease, while the Pauli paramagnetic susceptibility X(0) in the LT phase increases, resulting in suppression of the valence transition at x=0.3, indicating that the state of Yb3+ is stabilized down to very low temperatures. We found that the Kondo temperature TK of the LT phase is proportional to Tv according to the susceptibility measurements, which means that the stability of intermediate valence phase would be reduced by the Y substitution. According to the high field magnetization measurements in the range of T<Tv, Hv is decreased with increasing temperature.
