Volume effects and pressure effects on ferromagnetic superconductors

Thermal expansion of ferromagnetic superconductors below the superconducting transition temperature Tscu of a majority spin conduction band is re-examined. In the previous study [J.Phys.Conf .Ser. 200 012056 (2010)] the volume differential of the kinetic energy of conduction electrons is constant. In this study, the volume differential of the kinetic energy of conduction electrons is inconstant, however. The superconducting gaps used in this study are like those of the thin film of A2 phase in liquid 3He. We find that the thermal expansion coefficient has the divergence at the superconducting transition temperatures. Thermodynamic Grueneisen's relation is satisfied. The pressure effects on the superconductors are also investigated. As an example, the pressure differential of the superconducting transition temperatures and that of the Curie temperature are studied. We find the analytical expression of the pressure differential of the superconducting transition temperatures and that of the Curie temperature.