We report the first experimental observation of the two-node thickness dependence of the critical current in Josephson junctions with a ferromagnetic interlayer. Nodes of the critical current correspond to the transitions into the $\pi$ state and back into the conventional 0 state. From the experimental data the superconducting order parameter oscillation period and the pair decay length in the ferromagnet are extracted reliably. We develop a theoretical approach based on the Usadel equations taking into account the spin-flip scattering. Results of numerical calculations are in good agreement with experiments.

• Received 20 August 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.197003