Magneto-optical effect of films with nano-clustered cobalt particles dispersed in PMMA plastics

The magneto-optical effect of films comprising ultrafine fcc cobalt particles dispersed in a plastic (polymethyl methacrylate (PMMA)) matrix has been investigated. The cobalt particles were produced by decomposing dicobalt octacarbonyl [Co2(CO)8, shortly CO] at 110 °C in PMMA fluid dissolved by toluene. The average particle diameter, ranging from 5 to 30 nm, was controlled by the CO-concentration in PMMA. Droplets of the fluid were spread on glass plates by a spinning disc and were dried by evacuating toluene at room temperature. The films obtained were several micrometers thick and show high transmissivity. During solidification, a dc field was applied in the film plane to form cobalt particle filaments. Magneto-optical effect in the transmission mode in the wavelength interval between 300 and 900 nm were measured. The Faraday effect strongly depends upon the aggregation state of the cobalt particle clusters as well as the direction of linearly polarized incident light with respect to the cluster orientation, underwent a great change, being quite different from those of cobalt and PMMA.