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Terahertz-Range Polar Modes in Domain-Engineered BiFeO3

J.Hlinka1, M.Paściak1, S.Körbel1, P.Marton1

The dielectric permittivity and properties of electrically active lattice resonances in nanotwinned BiFeO3 crystals have been studied theoretically using an earlier established interatomic potential. The results suggest that an array of 71° domain walls with about 2–5 nm spacing enhances the static permittivity of BiFeO3 by more than an order of magnitude. This enhancement is associated with an electrically active excitation, corresponding to a collective vibration of pinned domain walls at a remarkably high frequency of about 0.3 THz.

Dispersion curves calculated for the monodomain [(a), left] and 71° domain wall [(b), right] structure of Fig. 1. The color scale indicates the projection onto the r component of the Last-type mode with the wave vector q along the s direction, with hotter colors marking a bigger participation ratio.

1Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8, Czech Republic