The Role of Multiferroics in the Negative Index of Refraction

We explore the possibility of realizing intrinsic far infrared negative index materials (NIM) in multiferroic crystals (crystals simultaneously possessing a ferroelectric and ferromagnetic phase) possessing electric and magnetic dipole resonances with nearby resonance frequencies, or overlapping regions of negative permittivity and permeability. We demonstrate the functionality of such a material using finite difference time domain simulations. In order to motivate the connection between multiferroics and negative index materials, we discuss the negative index of refraction in the polariton picture.