Our studies of the Brillouin scattering (BLS) from thermal magnons have revealed in arrays of Co nanowires with the diameter below 5 nm in a CeO2 matrix prepared by laser ablation a novel generation of metamaterials characterized by the following original feature. While their overall optical behavior is entirely conventional and thus reliably described by the Maxwell-Garnett approximation, in magneto-optical interactions they behave as negative refraction materials. This is explained by a peculiar quasi-circular polarization of light induced within the wires that has been identified through observation and further theoretical analysis of the reversed Stokes/anti-Stokes (S/AS) scattering asymmetry. In particular, the circular polarization degree has the opposite sign and a much larger absolute value than for the bulk Co film or thick Co wires. This reveals the great potential of seemingly simple wire arrays to manipulate the light at the nanoscale.