Phase and spin dynamics in a superconductor/ferromagnet/superconductor junction

We study a phase dynamics induced by a spin dynamics in a ferromagnetic Josephson junction, in which two superconductors (SC's) are separated by a ferromagnetic layer. A new phenomenological model for the phase variable is proposed by including the spin dynamics excited by the ferromagnetic resonance (FMR) in the gauge invariant phase of s-wave SC's. We found that the current-voltage characteristics show step structures by tuning the microwave frequency to FMR. The result originats from the coupling between the spin and the phase dynamics, and provides a new route to observe the spin wave excitation by using the Josephson effect.