Pressure Dependence of the Valence Phase Transition in YbInCu₄

Abstract

The valence phase transition of YbInCu₄ has been investigated by neutron diffraction and high pressure experiments. Rietveld refinement of the crystal structure has showed that the transition occurs with no change in crystal symmetry in a temperature range of about 35-50 K. The transition temperature T_v decreases linearly at a rate of -17 K/GPa with increasing the pressure up to 1 GPa, above which it decreases much faster up to 1. 75GPa. By using the bulk modules of YbInCu₄, a Grüneisen type parameter of η=dln (T_v) /dln (V (p) ), which represents the dependence of T_v on the volume V (p) is estimated as -64. This value of η is discussed in a relation to the Kondo volume collapse model for the α-γ transition of Ce metal.