Neutron and X-Ray Diffraction Studies of a Valence Fluctuating Compound YbInCu₄

Abstract

The crystal structure of YbInCu 4 has been refined by the Rietveld analysis of TOF neutron powder diffraction data. This compound has a cubic AuBe 5 (C15b, F\bar43m)-type structure with the lattice constant a =7.1575(6) Å, and Yb ions are completely ordered at the 4c site. X-ray powder diffraction data have also been taken as a function of temperature. The lattice constant shows an abrupt change of 0.15% at the temperature of Yb valence phase transition (about 40 K) without any change in the crystal symmetry.