Optical and magneto-optical properties of Co–SiOx thin films

The optical and magneto-optical properties of hybrid Co–SiOx systems are studied as a function of Co concentration. The structures were prepared by alternate depositions of SiOx thin films and layers of 10-nm-diameter Co nanoparticles produced by an Ion Cluster Source. Both optical and magneto-optical constants of the system gradually increase with the amount of Co, though maintaining low optical absorption values in the visible range. The experimental results are well reproduced assuming that the nanoparticles have a cobalt core (7–8 nm in diameter) surrounded by a cobalt oxide shell (1–2 nm thick). The magneto-optical activity versus optical absorption figure of merit of this system is compared with other magneto-optical dielectric systems.