  The inverse Faraday effect (IFE) allows the generation of magnetic fields by
optical excitation only. Since its discovery in the 60s, it was believed that
only an elliptical or circular polarization could magnetize matter by this
magneto-optical phenomenon. Here, we demonstrate the generation of an IFE via a
linear polarization of light. This new physical concept results from the local
manipulation of light by a plasmonic nano-antenna. We demonstrate that a gold
nanorod excited by a linear polarization generates a non-zero magnetic field by
IFE when the incident polarization of the light is not parallel to the long
axis of the rod. We show that this dissymmetry generates hot spots of local
non-vanishing spin densities (local elliptical polarization state), introducing
the concept of super circular light, allowing this magnetization. Moreover, by
varying the angle of the incident linear polarization with respect to the
nano-antenna, we demonstrate the on-demand flipping of the magnetic field
orientation. Finally, this linear IFE generates a stationary magnetic field 25
times stronger than what a gold nanoparticle produces when excited by a
circular polarization and via a classical IFE. The creation of stationary
magnetic fields by IFE in a plasmonic nanostructure is nowadays the only
technique allowing the creation of ultra-short, intense magnetic field pulses
at the nanoscale. Thus, it finds applications in the ultrafast control of
magnetic domains with applications not only in data storage technologies but
also in research fields such as magnetic trapping, magnetic skyrmion, magnetic
circular dichroism, to spin control, spin precession, spin currents, and spin
waves, among others.
