Neutron scattering experiments on YbXCu4 and ErXCu4 (X=Au, Pd, and Ag)

Temperature-dependent neutron scattering experiments with incident energies in the range 3--50 meV have been performed on polycrystalline samples of the heavy-electron system YbXCu4, as well as the stable 4f-moment compounds ErXCu4 and the nonmagnetic reference materials LuXCu4, with X=Au, Pd, and Ag. The quasielastic linewidth of the YbXCu4 compounds is determined as a function of temperature. For YbAuCu4 a quantitative crystal-field analysis is applied to the observed inelastic response, while the data for the strongly 4f-delocalized compound YbAgCu4 are discussed in terms of a possible crystal-field interpretation and various theoretical models for heavy-electron systems