  The inverse Faraday effect is a magneto-optical process allowing the
magnetization of matter by an optical excitation carrying a non-zero spin or
orbital moment of light. This phenomenon was considered until now as symmetric;
right or left circular polarizations generate magnetic fields oriented in the
direction of light propagation or in the counter-propagating direction. Here,
we demonstrate that by manipulating the spin density of light in a plasmonic
nanostructure, we generate a chiral inverse Faraday effect, creating a strong
magnetic field of 500 mT 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 data processing technologies.
