Friday, July 19, 2013

1305.3064 (Christelle Kadlec et al.)

Electromagnon in ferrimagnetic eps-Fe2O3 nanograin ceramics    [PDF]

Christelle Kadlec, Filip Kadlec, Veronica Goian, Marti Gich, Martin Kempa, Stephane Rols, Maxim Savinov, Jan Prokleska, Milan Orlita, Stanislav Kamba
Electromagnons are known from multiferroics as spin waves excited by the electric component of electromagnetic radiation. We report the discovery of an electromagnon in the far-infrared spectra of eps-Fe2O3 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 ferroelectricity in eps-Fe2O3 down to 10 K, despite its acentric (pyroelectric) crystal structure. This shows that the activation of electromagnons in the THz range 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 polarization analysis of THz and infrared spectra is possible.
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