Electromagnons are known from multiferroics as spin waves excited by the electric component of electromagnetic radiation. We report the discovery of an excitation in the far-infrared spectra of eps-Fe2O3 which we attribute to an electromagnon appearing below 110 K, where the ferrimagnetic structure becomes incommensurately modulated. Inelastic neutron scattering shows that the electromagnon energy corresponds to that of a magnon from the Brillouin zone boundary. Dielectric measurements did not reveal any sign of ferroelectricity in eps-Fe2O3 down to 10 K, despite its acentric crystal structure. This shows that the activation of an electromagnon requires, in addition to the polar ferrimagnetic structure, a modulation of the magnetic structure. We demonstrate that a combination of inelastic neutron scattering with infrared and / or terahertz spectroscopies allows detecting electromagnons in ceramics, where no crystal-orientation analysis of THz and infrared spectra is possible.
@article{arxiv.1305.3064,
title = {Electromagnon in ferrimagnetic eps-Fe2O3 nanograin ceramics},
author = {Christelle Kadlec and Filip Kadlec and Veronica Goian and Marti Gich and Martin Kempa and Stephane Rols and Maxim Savinov and Jan Prokleska and Milan Orlita and Stanislav Kamba},
journal= {arXiv preprint arXiv:1305.3064},
year = {2015}
}