Optical reflectivity and magnetoelectric effects on resonant plasmon modes in composite metal-multiferroic systems

The role of the magnetoelectric effect upon optical reflectivity is studied by adapting an electrodynamic-based model for a system composed by a 2D metallic film in contact with an extended multiferroic material exhibiting weak ferromagnetism. The well-known Nakayama's boundary condition is reformulated by taking into account the magnetoelectric coupling as well as an externally applied magnetic field B in an arbitrary direction. It is found that the reflectance shows strong fluctuations for incident radiation close to the characteristic antiferromagnetic resonance frequency associated with the multiferroic material in the THz regime. These results were verified for a 10 nm metallic foil by using a finite element method (FEM) and the Rouard's approach, for a wide range of wavelengths (0.1-5 mm), showing good agreement with respect to Nakayama's outcome, for the particular material BaMnF4.