Electric susceptibility of antiferromagnetic multiferroics with cycloidal spin order at magnetoelectric effect associated with collinear component of spins

TL;DR

This work investigates magnetoelectric coupling arising from the collinear spin component in antiferromagnetic multiferroics with cycloidal order and its impact on spin dynamics and dielectric response. Using a macroscopic Landau-Lifshitz-Gilbert framework combined with a spin-current polarization model, it derives analytic spin-wave dispersion and the frequency-dependent permittivity $\varepsilon(\omega)$, including the component $\varepsilon_{yy}$. Key contributions include explicit polarization expressions for ferromagnets and antiferromagnets, demonstration of electric-field control of exchange constants, and a delineation of Dzyaloshinsky-Moriya interaction effects on the spectra. The results show tunable spin-wave and dielectric properties via static electric fields in cycloidal multiferroics, with potential for electrically controllable magnonic and optoelectronic applications.

Abstract

The contribution of magnetoelectric effect to Landau--Lifshitz-Gilbert equation is considered in case when medium polarization is caused by parallel component of neighboring spins. The result is presented for ferromagnetic and antiferromagnetic materials. A comparison is given with the contribution of magnetoelectric effect to Landau--Lifshitz-Gilbert equation when medium polarization is caused by perpendicular component of spins. The dispersion dependence of spin waves in antiferromagnets with cycloidal equilibrium spin order is derived. The electric susceptibility and permittivity of antiferromagnetic multiferroics in which magnetoelectric effect is caused by collinear component of spins is obtained analytically.