  The present paper discusses magnon-mediated superconductivity in
ferromagnetic metals. The mechanism explains in a natural way the fact that the
superconductivity in UGe_2, ZrZn_2 and URhGe is apparently confined to the
ferromagnetic phase.The order parameter is a spin anti-parallel component ofa
spin-1 triplet with zero spin projection. The transverse spinfluctuations are
pair forming and the longitudinal ones are pair breaking.The competition
between magnons and paramagnons explains the existence of two successive
quantum phase transitions in UGe_2, from ferromagnetism to ferromagnetic
superconductivity, and at higher pressure to paramagnetism. The maximum T_{SC}
results from the suppression of the paramagnon contribution. To form a Cooper
pair an electron transfers from one Fermi surface to the other. As a result,
the onset of superconductivity leads to the appearance of two Fermi surfaces in
each of the spin up and spin down momentum distribution functions. This fact
explains the linear temperaturedependence at low temperature of the specific
heat, and the experimental results for UGe_2.
