pi-0 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. (C) 2001 MAIK Nauka / Interperiodica.