Neutron scattering experiments on YbXCu4and 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 YbX${\mathrm{Cu}}_4$, as well as the stable 4f-moment compounds ErX${\mathrm{Cu}}_4$ and the nonmagnetic reference materials LuX${\mathrm{Cu}}_4$, with X=Au, Pd, and Ag. The quasielastic linewidth of the YbX${\mathrm{Cu}}_4$ compounds is determined as a function of temperature. For ${\mathrm{YbAuCu}}_4$ a quantitative crystal-field analysis is applied to the observed inelastic response, while the data for the strongly 4f-delocalized compound ${\mathrm{YbAgCu}}_4$ are discussed in terms of a possible crystal-field interpretation and various theoretical models for heavy-electron systems.