  We unravel the underlying near-field mechanism of the enhancement of the
magneto-optical activity of bismuth-substituted yttrium iron garnet films
(Bi:YIG) loaded with gold nanoparticles. The experimental results show that the
embedded gold nanoparticles lead to a broadband enhancement of the
magneto-optical activity with respect to the activity of the bare Bi:YIG films.
Full vectorial near- and far-field simulations demonstrate that this broadband
enhancement is the result of a magneto-optically enabled cross-talking of
orthogonal localized plasmon resonances. Our results pave the way to the
on-demand design of the magneto-optical properties of hybrid magneto-plasmonic
circuitry.
