  Employing the self-consistent Green's function approach, we studied the
temperature dependence of the spin-wave stiffness in diluted magnetic
semiconductors. Note that the Green's function approach includes the spatial
and temperature fluctuations simultaneously which was not possible within
conventional Weiss mean-field theory. It is rather interesting that we found
the stiffness becomes dramatically softened as the critical temperature is
approached, which seems to explain the mysterious sharp drop of magnetization
curves in samples within diffusive regime.
