Far-infrared optical excitations in multiferroic TbMnO3 |
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| Authors: | M. Schmidt Ch. Kant T. Rudolf F. Mayr A. A. Mukhin A. M. Balbashov J. Deisenhofer A. Loidl |
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| Affiliation: | (1) Institute of Technical Sciences SASA, Knez Mihajlova 35/IV, 11000 Belgrade, Serbia;(2) Solid State Section, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece;(3) Institute for Multidisciplinary Research, Kneza Viseslava 1, 11000 Belgrade, Serbia;(4) Faculty of Electrical Engineering, University of Belgrade, Bulevar kralja Aleksandra 73, 11000 Belgrade, Serbia |
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| Abstract: | We provide a detailed study of the reflectivity of multiferroic TbMnO3 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. |
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