Mass enhancement and reentrant ground state under magnetic field in heavy fermion superconductors

Three different cases of magnetic field induced reentrant ground states in heavy fermion systems URhGe, UGe₂ and CeRhIn₅, recently studied in Grenoble, are discussed. URhGe is a ferromagnetic superconductor with the reentrace of superconductivity under magnetic field (H) which is associated to a spin reorientation. In the ferromagnetic superconductor UGe₂ an enhancement of the superconducting upper critical field H_c2 appears at its metamagnetic transition between two ferromagnetic phases. CeRhIn ₅ is a superconductor under high pressure and reentrance of antiferromagnetism is induced by magnetic field. We analyze the links between the H enhancement of the different contributions to the effective mass and the field reentrant phase.