Magneto-optical activity in resonant magnetoplasmonic disks

Metal-dielectric plasmonic nanodisks show a rich optical behaviour with the appearance of two modes of magnetic and electric dipolar character due to the interaction between the disks. These modes couple to the incident light in a different way, giving rise to regions with low and high optical extinction, respectively. Moreover, the insertion of a ferromagnetic component inside the structure introduces magneto-optical activity in the system[1]. As a consequence, metal-dielectric magnetoplasmonic nanodisks exhibit a rich optical and MO spectral phenomenology. It has previously been shown that, in Au/Co/Au nanodisks where a SiO2 layer is inserted, it is possible to obtain nanodisk configurations for which low optical absorption and large MO activity occur at the same spectral range. This is basically achieved by an adequate positioning of the dielectric component within the structure [2]. Here we present our study on the influence that the dielectric spacer thickness has on the interaction between the disks, and as a consequence, on the optical and MO properties of such structures [3,4]. The structures consist of a pure Au nanodisk separated by a SiO2 spacer from a MO component constituted by a 4nmAu/2nmCo multilayer nanodisk, which exhibits perpendicular magnetic anisotropy, reducing the required magnetic field to achieve saturation in polar configuration