Peculiar properties of the Josephson junction at the transition from 0 to π state -: art. no. 100501

It is demonstrated that in the diffusive superconductor-ferromagnet-superconductor (S/F/S) junctions the current-phase relation is practically sinusoidal everywhere except in a narrow region near the 0-pi transition. In this region the second harmonic dominates the scenario of the 0-pi transition. We predict a first-order transition for the S/F/S junctions with a homogeneous F barrier. However, in real junctions a small modulation of the thickness of the barrier may favor the continuous 0-pi transition and the realization of the Josephson junction with an arbitrary ground-state phase difference. The performed calculations of the second-harmonic amplitude provide a natural explanation of the recent contradictory results on the second-harmonic measurements.