Plasmonic magneto-optical nested 2D nanostructures: Tailoring responses through effective refractive index

•The magneto-optical response considerably increases due to the plasmon resonances.•In nested 2D nanostructures, the sign of polarization rotation can be inverted.•Due to the nested arrangement, the responses of can be strongly altered. Nested square 2D lattice of gold nanospheres encased in a film of bismuth-substituted yttrium iron garnet (Bi:YIG) have been studied. Symmetry, structural and dielectric parameters of such nanostructures have been found to define the number of plasmon resonances and their spectral positions. As compared with a conventional film of Bi:YIG, the magneto-optical response of the studied nanostructures considerably increases due to the plasmon resonances, and the sign of polarization rotation is defined by a configuration of the localized near fields. Also, we demonstrate that, due to the nested arrangement, the optical and magneto-optical responses of the nanostructures can be strongly altered with a negligible change in their structural parameters.