Stability of pi-phase in atomic-scale superconductor/magnet multilayered system

Atomic-scale superconductor/ferromagnet (S/F) and superconductor/antiferrom agnet (S/AF) multilayered systems are investigated in order to clarify the stability of the pi -phase,where the phase difference of the superconductin g (SC) order parameter between neighboring SC layers is pi. We clarify the stable region of this phase in the phase diagram with respect to temperatur e and exchange field (B) in magnetic layers. In the phase diagram, we show that the T-phase appears in both the S/F and S/AF cases. In particular, alt hough a previous work reported that the pi -phase is not obtained for any r easonable value of B in the S/AF case where the band structure in the norma l state of SC and magnetic lavers axe metallic and identical with each othe r, we find in this case that the stable region of the pi -phase is as wide as that in the S/F case under a certain condition. We also investigate how the pi -phase is affected by detailed band structures and the symmetry of S C order parameter, and discuss the possibility of this phase in the layered magnetic superconductor., RuSr2GdCu2O8.