  We numerically investigated the magnetic plasmon resonances in double-rod and
triple-rod structures (DRSs and TRSs, respectively) for sensing applications.
According to the equivalent circuit model, one magnetic plasmon mode was
induced in the DRS. Due to the hybridization effect, two magnetic plasmon modes
were obtained in the TRS. Compared with the electric plasmon resonance in a
single-rod structure (SRS), the electromagnetic fields near the DRS and TRS
were much more localized in the dielectric surrounding the structures at the
resonance wavelengths. This caused the magnetic plasmon resonance wavelengths
to become very sensitive to refractive index changes in the environment medium.
As a result, a large figure of merit that is much larger than the electric
plasmon modes of SRS could be obtained in the magnetic plasmon modes of DRS and
TRS. These magnetic plasmon mode properties enable the use of DRSs and TRSs as
sensing elements with remarkable performance.
