Anomalous Compressibility Associated with First Order Valence Change in YbInCu₄

抄録

Thermal expansion of the YbInCu₄ compound and volume anomaly ω_v associated with a sudden change of Yb valence v at T_v were measured under pressure up to 10 kbar. Both, the temperature T_v≈40 K and the anomaly ω_v = 0. 43% decrease under pressure linearly (with slopes dT_v/dp=-2. 2 K/kbar^-1 and dω_v /dp =-0. 021%kbar^-1) up to a critical pressure pc≅20 kbar. The compressibility κ increases below T_V, κ=1. 22 Mbar^-1 at 20K and κ= 0. 99 Mbar^-1 at 295 K. A derived pressure change of v (or f-shell occupation n_f), dv/dp≈0. 005 kbar^-1, leads to d lnV_Yb/dn_fƒ0. 15.