Eur. Phys. J. B (2014) 87: 232
https://doi.org/10.1140/epjb/e2014-50329-4

Regular Article

Lattice anharmonicity and polar soft mode in ferrimagnetic M-type hexaferrite BaFe₁₂O₁₉ single crystal

¹ Faculty of Physics, Southern Federal University, 344006 Rostov on Don, Russia
² Moscow Institute of Physics and Technology (State University), Dolgoprudny, 141700 Moscow Region, Russia
³ A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, 119991 Moscow, Russia
⁴ 1. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany
⁵ Moscow State Technical University of Radio engineering, Electronics and Automation, 119454 Russia

^a e-mail: a.mikheykin@sfedu.ru

Received: 22 May 2014
Received in final form: 29 June 2014
Published online: 15 October 2014

Abstract

The polar phonon modes in BaFe₁₂O₁₉ single crystal are studied in the temperature range from 6 to 300 K by polarized infrared spectroscopy. The phonon spectrum of the crystal is strongly anharmonic and unstable with respect to long-wavelength fluctuations of the dielectric permittivity along the hexagonal axis. Our results suggests that in BaFe₁₂O₁₉ hexaferrite symmetry lowering to the polar phase with the space group P6₃mc can be expected.