Neutron-inelastic-scattering study of the compound YbCuAl

Neutron-inelastic-scattering measurements on the compound YbCuAl reveal well-defined inelastic-scattering magnetic-response peaks superposed over a broad quasielastic-scattering spectrum at low temperatures. The inelastic-scattering peaks disappear around the temperature at which the maximum in the static susceptibility occurs (\ensuremath{\sim}30 K), above which the full spectral response can be described by a single quasielastic-scattering Lorentzian spectrum. The quasielastic-scattering spectral width increases again below 30 K, following the same trend as the spin fluctuation rate ${\ensuremath{\tau}}_{\mathrm{eff}{}^{\mathrm{\ensuremath{-}}1}}$ obtained from NMR measurements.