Direct dynamical coupling of spin modes and singlet Josephson supercurrent in ferromagnetic Josephson junctions

Abstract : Via a direct coupling between the order parameter and the singlet Josephson supercurrent we detect spin-wave resonances and their dispersion in ferromagnetic Josephson junctions in which the usual insulating or metallic barrier is replaced with a weak ferromagnet. The coupling arises within the Fraunhofer interferential description of the Josephson effect because the magnetic layer acts as a time-dependent phase plate. A spin-wave resonance at a frequency omega(s) implies a dissipation that is reflected as a depression in the current-voltage curve of the Josephson junction when h omega(s)=2eV. We have thereby performed a resonance experiment on only 10(7) Ni atoms.