  We investigate thermodynamic phases, including the phase of coexistence of
superconductivity and ferromagnetism, the possible phase transitions of first
and second order, and the shape of the phase diagram in mean-field
approximation for a phenomenological model of spin-triplet ferromagnetic
superconductors. The results are discussed in view of application to metallic
ferromagnets as UGe$_2$, ZrZn$_2$, URhGe, and Fe.
