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

TL;DR

This paper investigates how the magnetoelectric effect influences optical reflectivity in a metal-multiferroic system, revealing strong fluctuations near the antiferromagnetic resonance frequency through modeling and numerical methods.

Contribution

It introduces a reformulated boundary condition incorporating magnetoelectric coupling and applies it to analyze reflectivity in a metal-multiferroic interface, validated by numerical simulations.

Findings

Reflectance exhibits strong fluctuations near the antiferromagnetic resonance frequency.

The model's predictions agree well with finite element and Rouard's method simulations.

Magnetoelectric effects significantly impact optical properties in the THz regime.

Abstract

The r\^{o}le 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 \emph{Nakayama's} boundary condition is reformulated by taking into account the magnetoelectric coupling as well as an externally applied magnetic field $\mathbf{B}$ 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 BaMnF$_4$.