Surface-enhanced magneto-optics in metallic multilayer films

The magneto-optical properties noble-metal-ferromagnetic-metal multilayer thin films have been investigated as a function of the incidence angle, including the total reflection range, in the polar, longitudinal, and equatorial geometries, and for different values of the photon energy in the near-infrared and visible spectrum. The experimental and theoretical results are obtained on a Au/Co/Au model system. They demonstrate that the resonant coupling of the p component of the light electric field with the gold surface plasmon, which occurs in the total reflection range, yields a strong enhancement of the magneto-optical response and signal-to-noise ratio of the system for the three magnetization directions. This resonant coupling and the resulting enhancement of the relevant magneto-optical quantities are achieved for any photon energy in the near infrared and visible range simply by tuning the incidence angle. The efficiency of this enhancement effect is shown to increase towards the infrared region of the spectrum following the rise of the quality factor of the surface plasmon resonance.