  We study nonlinear response of conventional superconducting alloys with weak
magnetic impurities to an external alternating electromagnetic field. In
particular, we calculate a correction to superconducting order parameter up to
the second order in external vector potential. We show that frequency
dependence of the order parameter amplitude has characteristic resonant shape
with a maximum at frequency which is smaller than twice the magnitude of the
pairing amplitude in equilibrium and at the same time exceeds the
single-particle threshold energy. Our results suggest that in the presence of
magnetic impurities the dynamics of the pairing amplitude in the collisionless
regime will remain robust with respect to dissipative processes. We also
evaluate the third harmonic contribution to the current as a function of the
probe frequency and for various concentrations of magnetic impurities.
