Surface plasmon-assisted control of the phase of photo-induced spin precession

We demonstrate surface plasmon-assisted control of a photo-magnetic spin precession phase in hybrid noble metal-dielectric magneto-plasmonic crystals. The plasmon-driven photo-magnetic excitation of the spin precession in the dielectric was performed by means of a time-resolved magneto-optical method in the near-infrared spectral range. We show, both experimentally and numerically, that a surface plasmon-polariton resonance results in the phase reversal of the spin precession. We discuss the similarity of plasmonic excitations in metal-dielectric bilayers to the action of photo-magnetic stimuli with orthogonal linear polarization in dielectrics. These results demonstrate rich possibilities of plasmonic excitations beyond conventional enhancement of the electric field intensity and indicate high promise of magneto-plasmonics for photo-magnetism at the nanoscale.