Diamagnetic nature of stratified thin metals in visible range

It is numerically demonstrated that effectively strong diamagnetic resonance emerges at visible frequencies in stratified metal-dielectric metamaterials. The effective optical constants are extracted by two-complex reflectivity method. It is clarified that the effective diamagnetic response originates from local diamagnetism at stratified thin metals. The effective diamagnetism is crucially sensitive to the sturucture of unitcell. The effective diamagnetic response is always associated with effective plasma frequency and is therefore regarded as a magnetic component of the collective excitation.