Tunable magnetic resonances of high-permittivity dielectric rings coated with graphene

We consider a planar resonator made of a thin, high-permittivity dielectric ring coated on one side with graphene. It is shown that the resonant magnetic response of the ring to an axially applied time-harmonic magnetic field can be efficiently controlled by electrical gating of the graphene coating. Variations of the resonance frequencies and quality factors with the Fermi energy of graphene are investigated for the micrometer- and centimeter-size rings operating in the terahertz and gigahertz frequency ranges.