  To describe anomalous zone-boundary softening and damping of magnons in
manganites we present a phenomenological two-fluid model containing
ferromagnetic Fermi-liquid and non-Fermi-liquid components. The Fermi-liquid
component accounts for softening of zone-boundary magnons and for the Landau
damping of magnons in the Stoner continuum arising at low frequencies due to
zero-point effects. Coupling of the Fermi-liquid and non-Fermi-liquid fluids
yields conventional long wavelength magnons damped due to their coupling with
longitudinal spin fluctuations.
