Magneto-optical Faraday activity in transparent FeCo-sepiolite/polystyrene nanocomposites

FeCo nanoparticles synthesized on sepiolite microparticles were used for the preparation of nanocomposites by melt compounding with polystyrene. Both, the sepiolite fibers and the nanoparticles were free of agglomeration, which allowed preparing nanocomposites with a homogeneous dispersion of the second phases, avoiding the usual agglomeration of the nanoparticles and minimizing light scattering. As a consequence, transparent composites with a high magnetic susceptibility have been obtained. The magneto-optical Faraday activity of these nanocomposites has been studied, finding saturation rotations over 200 rad·m−1 in the visible range. The processing route presented in this work can be easily transferred to industry and allows preparing polymer matrix nanocomposites with no restriction on shape or size and opens the possibility of developing other highly transparent polymer-based nanocomposites.