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Abstracts
The boracites with general formula M_3B_7O_{13}X (M = divalent metal, X = Cl, Br, I), shortly denoted as M-X, are among the first known multiferroic materials. They exhibit a sequence of transitions from the high temperature paraelectric cubic phase to ferroelectric orthorhombic, monoclinic, trigonal phases, and finally to a monoclinic phase at low temperatures, where both ferroelectric and magnetic orders coexist. The lattice dynamics of boracites has been scarcely studied with the Raman spectroscopy, the main problem with non-cubic phases being the coexistence of twin variants with different crystallographic and polarization orientation. In this work, on the example of Co_3B_7O_{13}Cl (Co-Cl), Co_3B_7O_{13}Br (Co-Br) and Ni_3B_7O_{13}Br (Ni-Br) we demonstrate that using the Raman microscopy imaging one can visualize the twin variants, follow their transformation through the crystallographic transitions, obtain Raman spectra from untwinned domains in exact scattering configurations, determine the Raman mode symmetries, and assign Raman lines to definite atomic motions. The effects of structural transitions and elemental substitution are discussed in close comparison with results of ab initio calculations of the phonon structure of the cubic phase.
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Journal
Year
Volume
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Pages
19-24
Physical description
Dates
published
2009-07
Contributors
author
- Texas Center for Superconductivity, University of Houston, Houston TX 77204-5002, USA
author
- Texas Center for Superconductivity, University of Houston, Houston TX 77204-5002, USA
author
- Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), 08193 Bellaterra (Barcelona), Spain
author
- Institut Català de Nanotecnologia (ICN) Edifici CM7, Campus de la UAB 08193 Bellaterra (Barcelona), Spain
- Departament de Física Edifici Cn Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
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Document Type
Publication order reference
Identifiers
YADDA identifier
bwmeta1.element.bwnjournal-article-appv116n103kz