Artificial magnetism of cross shaped metamaterial in green light frequencies

•A negative permeability and negative refractive index over 50 THz is obtained.•A high figure of merit reaching 3.75 is obtained at green light range.•Strong magnetic field enhancement is archived at magnetic resonance.•The magnetic resonance is tuned both in frequency and resonance strength.

We theoretically investigate the magnetic response of a cross-shaped metamaterial at green light frequencies. Such a structure supports a strong magnetic resonance, which results in a large negative permeability and hence a band of negative refractive index over 50 THz. The structure is low loss and exhibits a high FOM of 3.75 at 570 THz. The magnetic resonance can be effectively tailored both in operation frequency and resonance strength by means of adjusting the geometric dimensions, which is well described by the equivalent circuit model. The proposed structure may offer an effective means to realize the magnetic devices at visible frequencies.