Electromagnons in multiferroic RMn2O5 compounds and their microscopic origin

TL;DR

This paper reviews electromagnons in multiferroic RMn2O5 compounds, proposing a microscopic model based on isotropic Heisenberg exchange and magnetostrictive coupling, explaining various magnetic and optical phenomena without relativistic effects.

Contribution

It introduces a realistic microscopic model for electromagnons in RMn2O5 compounds that accounts for their magnetic and optical properties without involving relativistic interactions.

Findings

The model explains the spin re-orientation transition.

It accounts for electromagnon peaks in non-collinear spin states.

It describes the polarization of light associated with electromagnons.

Abstract

We summarize the existing experimental data on electromagnons in multiferroic RMn2O5 compounds, where R denotes a rare earth ion, Y or Bi, and discuss a realistic microscopic model of these materials based on assumption that the microscopic mechanism of magnetically-induced ferroelectricity and electromagnon absorption relies entirely on the isotropic Heisenberg exchange and magnetostrictive coupling of spins to a polar lattice mode and does not involve relativistic effects. This model explains many magnetic and optical properties of RMn2O5 manganites, such as the spin re-orientation transition, magnetically-induced polarisation, appearance of the electromagnon peak in the non-collinear spin state and the polarisation of light for which this peak is observed. We compare experimental and theoretical results on electromagnons in RMn2O5 and RMnO3 compounds.