Stability of π-Phase in Atomic-Scale Superconductor/Magnet Multilayered System

Atomic-scale superconductor/ferromagnet (S/F) and superconductor/antiferromagnet (S/AF) multilayered systems are investigated in order to clarify the stability of the π-phase where the phase difference of the superconducting (SC) order parameter between neighboring SC layers is π. We clarify the stable region of this phase in the phase diagram with respect to temperature and exchange field (B) in magnetic layers. In the phase diagram, we show that the π-phase appears in both the S/F and S/AF cases. In particular, although a previous work reported that the π-phase is not obtained for any reasonable value of B in the S/AF case where the band structure in the normal state of SC and magnetic layers are metallic and identical with each other, we find in this case that the stable region of the π-phase is as wide as that in the S/F case under a certain condition. We also investigate how the π-phase is affected by detailed band structures and the symmetry of SC order parameter, and discuss the possibility of this phase in the layered magnetic superconductor, RuSr₂GdCu₂O₈.