Shape-enhanced magneto-optical activity: Degree of freedom for active plasmonics

Magnetoplasmonic nanostructures with enhanced magneto-optical (MO) activity hold great promise for the active manipulation of plasmon propagation. In this Rapid Communication, we demonstrate that the shape of elliptical nanocylinder plays an essential role on the large enhanced MO activity: (1) saturated MO activity component depends on the angle of polarization plane of incident light with respect to the semimajor axis of elliptical nanocylinder and (2) a low magnetic field induces MO activity with nonferromagnetic origin exhibiting a giant linear component added to the saturated component in the MO loops. The intriguing optical and MO properties were well interpreted within one model by assigning a biaxial effective permittivity tensor to the elliptical nanocylinder array. It is suggested that the shape enhanced MO activity can be maximized by elaborately tuning the plasmon resonance as well as increasing the aspect ratio of elliptical nanocylinder.