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Advances in Condensed Matter Physics
Volume 2013 (2013), Article ID 104806, 13 pages
http://dx.doi.org/10.1155/2013/104806
Review Article

Understanding Multiferroic Hexagonal Manganites by Static and Ultrafast Optical Spectroscopy

1Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
2Advanced Ultrafast Laser Research Center, University of Electro-Communications, Chofugaoka 1-5-1, Chofu, Tokyo 182-8585, Japan

Received 25 June 2012; Revised 19 January 2013; Accepted 28 January 2013

Academic Editor: R. N. P. Choudhary

Copyright © 2013 Yu Ting Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Multiferroic hexagonal manganites ReMnO3 studied by optics are reviewed. Their electronic structures were revealed by static linear and nonlinear spectra. Two transitions located at 1.7 eV and 2.3 eV have been observed and attributed to the interband transitions from the lower-lying Mn3+ and states to the Mn3+ state, respectively. These so-called d-d transitions exhibit a blueshift as decreasing temperatures and an extra blueshift near . This dramatic change indicates that the magnetic ordering seriously influences the electronic structure. On the other hand, the ultrafast optical pump-probe spectroscopy has provided the important information on spin-charge coupling and spin-lattice coupling. Because of the strongly correlation between electronic structure and magnetic ordering, the amplitude of the initial rising component in shows striking changes at the vicinity of . Moreover, the coherent optical and acoustic phonons were observed on optical pump-probe spectroscopy. Both the amplitude and dephasing time of coherent phonons also exhibit significant changes at , which provide the evidence for spin-lattice interaction in these intriguing materials.