Magnetic response in non-magnetic materials and coupled dipole interactions

Research into the fabrication of negative permeability and negative index metamaterials has focused on intricately-shaped metallic constituent particles. However, a simpler design for a magnetic metamaterial could instead use non-magnetic spheres with a large permittivity [1]. This is possible because each sphere acts as a cavity resonator with a fundamental magnetic dipole resonance, operating in the long wavelength limit due to the large permittivity. Furthermore, coating the spheres with a metal or semiconductor shell would result in a negative index metamaterial [2]. Depending on the choice of materials, this design can be applied at microwave, infrared, or visible frequencies.