We study the spin-wave dispersion of localized spins in a disordered
double-exchange model using the perturbation theory with respect to the
strength of the disorder potential. We calculate the dispersion upto the
next-leading order, and extensively examine the case of one-dimension. We show
that in that case, disorder yields anomalous gapped-like behavior at the Fermi
wavenumber of the conduction electrons.Comment: 9 pages, 5 figure