  We demonstrate resonant Faraday polarization rotation in plasmonic arrays of
bimetallic nano-ring resonators consisting of Au and Ni sections. This
metamaterial design allows to optimize the trade-off between the enhancement of
magneto-optical effects and plasmonic dissipation. Although Ni sections
correspond to as little as ~6% of the total surface of the metamaterial, the
resulting magneto-optically induced polarization rotation is equal to that of a
continuous film. Such bimetallic metamaterials can be used in compact magnetic
sensors, active plasmonic components and integrated photonic circuits.
