Regensburg 2019 – wissenschaftliches Programm
MA 7.8: Vortrag
Montag, 1. April 2019, 17:15–17:30, H37
THz and SANS study of magnons in BiFeO3 — •Dániel Gergely Farkas1, Dávid Szaller1, 2, István Kézsmárki1, 3, Laur Peedu4, Johan Viirok4, Urmas Nagel4, Toomas Rõõm4, and Sándor Bordács1 — 1Department of Physics, BUTE, Hungary — 2Institute of Solid State Physics, TU Wien, Austria — 3Experimental Physics V., UA, Augsburg, Germany — 4NICPB, Tallinn, Estonia
Multiferroic materials with coexisting and strongly coupled magnetic and ferroelectric orders have attracted much interest due to the novel phenomena they possess, such as magnetoelectric effect  and directional dichroism . Among these compounds BiFeO3 has received special attention as it is one of the few known room-temperature multiferroics . Previously we showed by using THz spectroscopy that in contrast to the theoretical models the (111) plane of BiFeO3 is almost isotropic and the magnetic field dependence of the excitation frequencies have hysteresis. With small angle neutron scattering (SANS) measurements we determined the low temperature behavior of the magnetic domains in external magnetic fields , which helped in the interpretation of the THz data. The improved picture of the magnetic domains supports all THz results including the isotropic (111) plane, selection rules and hysteresis of the mode frequencies. References:  M. Tokunaga, et al., Nat. Commun. 6, 5878 (2015).  I. Kézsmárki, et al., Phys. Rev. Lett. 106, 057403 (2011).  J. Moreau, et al., J. Phys. Chem. Solids 32, 1315 (1971).  S. Bordács, et al., Phys. Rev. Lett. 120, 147203 (2018).