  Via a direct coupling between the magnetic 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 ws implies a dissipation that is reflected as a depression in the
current-voltage curve of the Josephson junction when hbar ws = 2eV. We have
thereby performed a resonance experiment on only 10^7 Ni atoms.
