Magnetically Tunable Invisibility of a Homogeneous Dielectric Rod with No Cover or Active Source

We demonstrate the invisibility of a homogeneous ferrite rod and photonic crystals composed of such rods when an appropriate external static magnetic field (ESMF) is applied. As a naturally occurring effect, no external tool, including metamaterial and plasmonic covers or active sources, is used to hide the rod. In the invisible state, the response of the rod to the impinging wave becomes unique, with a 1/4-cycle response delay of the induced magnetic dipole which lowers its scattering efficiency to the maximum possible extent. The visible and invisible states can be manipulated by an ESMF. The manipulability enables photonic crystals composed of such rods to assume different functions in the same electromagnetic device, such as remaining transparent for the impinging wave or totally reflecting it. The fast switching time of magnetic systems might make it particularly useful for practical applications.