Dresden 2017 – wissenschaftliches Programm
DF 18.1: Vortrag
Donnerstag, 23. März 2017, 15:00–15:15, WIL B321
THz study of the magnon spectra of BiFeO3 — •Dániel Gergely Farkas1, Sándor Bordács1, Dávid Szaller1, Laur Peedu2, Johan Viirok2, Urmas Nagel2, Toomas Rõõm2, and István Kézsmárki1 — 1Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary — 2National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 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 , which puts its technical applications within reach. Here we present an experimental study of the magnon excitations in single crystal samples of BiFeO3. Using THz spectroscopy magnetic field dependence of the spin-wave frequencies are measured along all three high-symmetry axis up to 33T. This systematic study also allowed us to determine the electric and magnetic dipole strengths, i.e. the selection rules. In contrast to the previous theoretical models we found that the (111) plane of BiFeO3 is isotropic and the magnetic field dependence of the excitation frequencies have hysteresis. 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).