Surface Plasmon Resonance Effects in the Magneto-Optical Activity of Ag-Co-Ag Trilayers

A complete magneto-optical characterization of Pt capped Ag-Co-Ag sputtered trilayers with varying Co thickness is presented. Polar Kerr rotation and ellipticity exhibit a gradual increase in signal as the Co layer gets thicker, with a sharp feature around 3.75 eV due to the bulk Ag plasmon resonance. The transverse Kerr signal of such trilayers is strongly affected by the surface plasmon polariton (SPP) resonance excitation when measured in the Kretschmann configuration, with a maximum transverse Kerr effect for around 2 nm Co thickness which corresponds to the optimum SPP excitation. This behavior is in contrast with the monotonous increase in transverse Kerr signal with Co thickness measured when the SPP is not excited. These results are in qualitative agreement with simulations using the transfer matrix formalism, the discrepancies mainly being due to the deviation from 2-D growth of the system and possible Ag and Co oxidation effects.