Valence transition in the intermetallic compound system Yb_1-xY_xInCu₄

At the transition temperature (T_v ≈ 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 (Yb^2.9+) 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 H_v ≈ 30 T. We will discuss the valence transition in the Yb_1-xY_xInCu₄ system by measurements of susceptibility and high field magnetization in this paper. With increasing x, T_v and H_v decrease, while the Pauli paramagnetic susceptibility χ(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 T_K of the LT phase is proportional to T_v 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 < T_v, H_v is decreased with increasing temperature.