14. Magnetochiral Metamolecules for Microwaves

This chapter overviews magnetochiral (MCh) effects for the X-band microwaves by a single metamolecule consisting of a copper chiral structure and a ferrite rod. The directional birefringence due to the MCh effects is induced at the resonant optical activity frequencies by applying a weak DC magnetic field of 1 mT and increased with the magnetic field. The nonreciprocal differences in refractive indices by the MCh effects are evaluated to be \(10^{-3}\) at 200 mT, which is much larger than that observed in natural chiral molecules at the visible frequencies. Moreover, the enhanced MCh effects can be obtained at ferromagnetic resonance frequencies by the ferrite rod in the metamolecule. The present study paves the way toward the realization of synthetic gauge fields for electromagnetic waves and the emergence of meta material-science using microwave metamaterials. Furthermore, higher frequencies including the visible region are accessible by our concept, in which an interaction between magnetism and chirality in the metamaterials is realized without intrinsic electronic interactions.