Regimes of optical transparency and instabilities of collinear dielectric ferromagnetic materials in the presence of the dynamic magnetoelectric effect

TL;DR

This paper investigates how dynamic magnetoelectric effects influence optical transparency and stability in collinear dielectric ferromagnetic materials, revealing regimes of transparency and instabilities linked to spin dynamics and electromagnetic wave polarization.

Contribution

It introduces a theoretical analysis of the regimes of optical transparency and instability caused by the dynamic magnetoelectric effect in collinear dielectric ferromagnetic materials.

Findings

Identifies frequency regimes where the refractive index approaches 1.

Discovers signs of instability in parallel spin configurations during electromagnetic wave propagation.

Shows the influence of magnetoelectric coupling on dielectric permeability and optical properties.

Abstract

The contribution of the polarization associated with the noncollinear parts of spins in the dielectric permeability tensor of multiferroic materials is considered. As the equilibrium state, we consider the systems of parallel spins, so we have zero equilibrium polarization. Dynamical polarization appears due to the spin evolution via the magnetoelectric coupling. The regime of frequencies, where the refractive index goes to 1 is found for the high (in comparison with the characteristic frequency of the anisotropic energy or the cyclotron frequency) left/right circularly polarized electromagnetic wave propagating parallel to the equilibrium spin direction. Moreover, the signs of the imaginary part of the dielectric permeability, the refractive index, and the frequency show the instability of the parallel spin configuration at the propagation of the linearly polarized electromagnetic wave due to the effective magnetoelectric interaction.