Far-infrared optical excitations in multiferroic TbMnO_3

Abstract

We provide a detailed study of the reflectivity of multiferroic TbMnO_3 for wave numbers from 40 cm^{-1} to 1000 cm^{-1} and temperatures 5 K < T < 300 K. Excitations are studied for polarization directions E || a, the polarization where electromagnons are observed, and for E || c, the direction of the spontaneous polarization in this material. The temperature dependencies of eigenfrequencies, damping constants and polar strengths of all modes are studied and analyzed. For E || a and below the spiral ordering temperature of about 27 K we observe a transfer of optical weight from phonon excitations to electromagnons, which mainly involves low-frequency phonons. For E || c an unusual increase of the total polar strength and hence of the dielectric constant is observed indicating significant transfer of dynamic charge probably within manganese-oxygen bonds on decreasing temperatures.

8 pages, 7 figures, accepted for submission in European Physical Journal B

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Cited by in corpus (11)

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• Magneto-electric excitations in multiferroic TbMnO3 by Raman scattering
• Elastic and magnetic effects on the infrared phonon spectra of MnF2
• Electromagnon in the Z-type hexaferrite $({\mathrm{Ba}}_x{\mathrm{Sr}}_{1-x}{)}_3\mathrm{C}{\mathrm{o}}_2\mathrm{F}{\mathrm{e}}_{24}{\mathrm{O}}_{41}$
• Electromagnon and phonon excitations in multiferroic TbMnO3
• Infrared-active phonon modes in monoclinic multiferroic MnWO4
• Infrared reflectivity of the phonon spectra in multiferroic TbMnO3
• Unravelling the role of Sm 4f electrons in the magnetism of SmFeO${}_3$
• Modifying the magnetoelectric coupling in TbMnO${}_3$ by low-level Fe${}^{3+}$ substitution
• Lattice dynamics and spin-phonon interaction in strained NiO films
• Spin-phonon interaction increased by compressive strain in antiferromagnetic MnO thin films