Isotropic 3D optical magnetism in visible light in a self-assembled metamaterial

Raspberry-like plasmonic nanoclusters have been synthesized by nanochemistry and self-assembled into bulk metamaterials in microfluidic devices. The optical properties of the nanoclusters have been studied by polarization resolved light scattering prior to assembling. The scattering efficiencies of the electric and magnetic multipoles are unambiguously determined experimentally, in excellent agreement with numerical simulations. The residual degree of anisotropy inherent to the self-assembly process is measured. The effective magnetic permeability of the assembled material differs notably from 1 and shows no significant dependence on the direction of propagation.