  The inverse Faraday effect is a magneto-optical process allowing the
magnetization of matter by an optical excitation carrying a non-zero spin of
light. In particular, a right circular polarization generates a magnetization
in the direction of light propagation and a left circular polarization in the
opposite direction to this propagation. We demonstrate here that by
manipulating the spin density of light, i.e., its polarization, in a plasmonic
nanostructure, we generate a reversed inverse Faraday effect. A right circular
polarization will generate a magnetization in the opposite direction of the
light propagation, a left circular polarization in the direction of
propagation. Also, we demonstrate that this new physical phenomenon is chiral,
generating a strong magnetic field only for one helicity of the light, the
opposite helicity producing this effect only for the mirror structure. This new
optical concept opens the way to the generation of magnetic fields with
unpolarized light, finding application in the ultrafast manipulation of
magnetic domains and processes, such as spin precession, spin currents, and
waves, magnetic skyrmion or magnetic circular dichroism, with direct
applications in data storage and processing technologies.
