Anisotropic Thermal Expansion Coefficients of CeCu₂ Single Crystal under High Pressure

Abstract

The thermal expansion coefficient α_i(T) of CeCu₂ single crystal has been measured up to 20 kbar in the temperature range from 4.2 K to 260 K in order to study the anisotropic behavior of the α_i(T) at high pressure. It is found that the contribution of the 4f electron to the α_i(T) shows an anisotropic behavior; i.e., α_a(T) and α_b(T) of CeCu₂ become similar to those of YCu₂ with the application of pressure, but α_c(T) of CeCu₂ differs greatly from that of YCu₂ at high pressure. A decrease in the density of states at the Fermi level is observed at high pressure. The result suggests a pressure-induced crossover from the concentrated Kondo state to the intermediate valence state.