Pi-o Transition in Superconductor-Ferromagnet-Superconductor Junctions

Superconductor ferromagnet superconductor (SFS) Josephson junctions are known to exhibit a transition between Pi and 0 states. In this letter, we find the Pi 0 phase diagram of an SFS junction depending on the transparency of an intermediate insulating layer (I). We show that, in general, the Josephson critical current is nonzero at the Pi 0 transition temperature. Contributions to the current from the two spin channels nearly compensate each other, and the first harmonic of the Josephson current as a function of phase difference is suppressed. However, higher harmonics give a nonzero contribution to the supercurrent