A new class of media with abnormal electromagnetic parameters has been attracting increasing attention because of its exotic properties and potential application.Currently,typical metamaterials are mainly composed of artificially designed metallic periodic structures.However,due to the limitations of available fabrication technologies,physical size and material effects,it is difficult to realize these abnormal properties by these artificial structures in the high-frequency regime.Therefore,it is important to find materials with intrinsic abnormal electromagnetic responses.In this field,a new mechanism based on the interaction between polar lattice vibrations and electromagnetic waves has been proposed.In this paper,we review progress in this field.
Isotropic negative permeability composite,composed of BST-MgO dielectric cubes with high permit-tivity dispersed in the Teflon substrate with low permittivity,was designed and fabricated based on Mie resonance and the effective medium theory.Measurements and simulations showed that the dielectric composite exhibited a strong sub-wavelength magnetic resonance at the first Mie resonance and possessed isotropic negative permeability,which resulted from the displacement current excited in the cubes.The dielectric particle was equivalent to a magnetic dipole at the magnetic resonance,which could be adjusted by the size and permittivity of the particles.It may provide a convenient method to design isotropic metamaterials and invisible cloak at infrared and visible frequencies.
