Abstract-Terahertz Spectroscopy of Spin Waves in Multiferroic BiFeO3 in High Magnetic Fields

U. Nagel^1,*, Randy S. Fishman², T. Katuwal^1,†, H. Engelkamp³, D. Talbayev⁴, Hee Taek Yi⁵, S.-W. Cheong⁵, and T. Rõõm^1
1National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
²Oak Ridge National Laboratory, Materials Science and Technology Division, Oak Ridge, Tennessee 37831, USA
³High Field Magnet Laboratory, Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands
⁴Department of Physics, Tulane University, 5032 Percival Stern Hall, New Orleans, Louisiana 70118, USA
⁵Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, New Jersey 08854, USA

Received 12 February 2013; revised 17 May 2013; published 17 June 2013

We have studied the magnetic field dependence of far-infrared active magnetic modes in a single ferroelectric domain BiFeO₃ crystal at low temperature. The modes soften close to the critical field of 18.8 T along the [001] (pseudocubic) axis, where the cycloidal structure changes to the homogeneous canted antiferromagnetic state and a new strong mode with linear field dependence appears that persists at least up to 31 T. A microscopic model that includes two Dzyaloshinskii-Moriya interactions and easy-axis anisotropy describes closely both the zero-field spectroscopic modes as well as their splitting and evolution in a magnetic field. The good agreement of theory with experiment suggests that the proposed model provides the foundation for future technological applications of this multiferroic material.

© 2013 American Physical Society