  We demonstrate that there is a long-range vortex-vortex attraction in
ferromagnetic superconductors due to polarization of the magnetic moments.
Vortex clusters are then stabilized in the ground state for low vortex
densities. The motion of vortex clusters driven by the Lorentz force excites
magnons. This regime becomes unstable at a threshold velocity above which
domain walls are generated for slow relaxation of the magnetic moments and the
vortex configuration becomes modulated. This dynamics of vortices and magnetic
moments can be probed by transport measurements.
