  The magneto-optical activity, namely the polarization conversion capabilities
of high-index, non-absorbing, core-shell dielectric nanospheres is
theoretically analyzed. We show that, in analogy with their plasmonic
counterparts, the polarization conversion in resonant dielectric particles is
linked to the amount of electromagnetic field probing the magneto-optical
material in the system. However, in strong contrast with plasmon nanoparticles,
due to the peculiar distribution of the internal fields in resonant dielectric
spheres, the magneto-optical response is fully governed by the magnetic
(dipolar and quadrupolar) resonances with little effect of the electric ones.
