Spectral dependence of the magnetic modulation of surface plasmon polaritons in noble/ferromagnetic/noble metal films

The magnetic field is an interesting candidate for the development of active plasmonic devices as it is able to modify the surface plasmon polariton (SPP) wave vector. Both real and imaginary parts of the SPP wave vector are affected. Here, we have experimentally determined the contribution of both modulations in the spectral range λ ₀=500-1000 nm for magnetoplasmonic systems consisting of noble/ferromagnetic/noble multilayered metal films. We have seen that the real part usually exceeds the imaginary one, but in the longer wavelength range the contribution of the imaginary part cannot be neglected. We have analyzed the spectral dependency of the modulation, and we conclude that it is dominated by the evolution of the SPP properties with wavelength and not the magneto-optical parameter. A figure of merit including modulation and propagation distance is also studied for the three ferromagnetic metals, Fe, Co, and Ni.