Identifying the Magnetoelectric Modes of Multiferroic BiFeO${}_3$

Abstract

We have identified three of the four magnetoelectric modes of multiferroic BiFeO${}_3$ measured using THz spectroscopy. Excellent agreement with the observed peaks is obtained by including the effects of easy-axis anisotropy along the direction of the electric polarization. By distorting the cycloidal spin state, anisotropy splits the ${\Psi }_{\pm 1}$ mode into peaks at 20 and 21.5 cm${}^{-1}$ and activates the lower ${\Phi }_{\pm 2}$ mode at 27 cm${}^{-1}$ (T=200 K). An electromagnon is identified with the upper ${\Psi }_{\pm 1}$ mode at 21.5 cm${}^{-1}$. Our results also explain recent Raman and inelastic neutron-scattering measurements.

5 pages, 4 Figures, Submitted to Physical Review Letters

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• Terahertz spectroscopy of spin waves in multiferroic BiFeO${}_3$ in high magnetic fields
• Temperature-Dependent Interplay of Dzyaloshinskii-Moriya Interaction and Single-Ion Anisotropy in Multiferroic BiFeO${}_3$
• Magnetic Interactions in BiFeO${}_3$: a First-Principles Study
• The Spin State and Spectroscopic Modes of Multiferroic BiFeO3
• Evidence for two spin-glass transitions with magnetoelastic and magnetoelectric couplings in the multiferroic (Bi${}_{1-x}$Ba${}_x$)(Fe${}_{1-x}$Ti${}_x$)O${}_3$ system
• Spin and lattice excitations of a BiFeO3 thin film and ceramics
• Field dependence of the Spin State and Spectroscopic Modes of Multiferroic BiFeO${}_3$
• Normal Modes of a Spin Cycloid or Helix
• Spin-current driven Dzyaloshinskii-Moriya interaction in the multiferroic BiFeO3 from first-principles
• Orientation Dependence of the Critical Magnetic Field for Multiferroic BiFeO${}_3$