Coexistence of superconductivity and ferromagnetism in ferromagnetic metals

We address the question of coexistence of superconductivity and ferromagnet ism. Using a field theoretical approach we study a one-fermion effective mo del of a ferromagnetic superconductor in which the quasiparticles responsib le for the ferromagnetism form the Cooper pairs as well. For the first time we solve self-consistently the mean-field equations for the superconductin g gap and the spontaneous magnetization. We discuss the physical features w hich are different in this model and the standard BCS model and consider th eir experimental consequences