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Emergence of central mode in the paraelectric phase of ferroelectric perovskites

Published online by Cambridge University Press:  12 February 2013

Jeevaka Weerasinghe
Affiliation:
Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701
L. Bellaiche
Affiliation:
Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701
T. Ostapchuk
Affiliation:
Institute of Physics, Academy of Sciences of the Czech Republic, 18221 Prague 8, Czech Republic
P. Kužel
Affiliation:
Institute of Physics, Academy of Sciences of the Czech Republic, 18221 Prague 8, Czech Republic
C. Kadlec
Affiliation:
Institute of Physics, Academy of Sciences of the Czech Republic, 18221 Prague 8, Czech Republic
S. Lisenkov
Affiliation:
Department of Physics, University of South Florida, Tampa, Florida 33620
I. Ponomareva
Affiliation:
Department of Physics, University of South Florida, Tampa, Florida 33620
J. Hlinka*
Affiliation:
Institute of Physics, Academy of Sciences of the Czech Republic, 18221 Prague 8, Czech Republic
*
Address all correspondence to J. Hlinka at [email protected]
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Abstract

THz-range dielectric spectroscopy and first-principle-based effective-Hamiltonian molecular dynamics simulations were used to elucidate the dielectric response in the paraelectric phase of (Ba, Sr)TiO3 solid solutions. Our analysis suggests a crossover between two regimes: a higher-temperature regime governed by the soft mode only versus a lower-temperature regime exhibiting a coupled soft mode/central mode dynamics. Interestingly, a single model can be used to adjust the THz dielectric response in the entire range of the paraelectric phase. The central peak cannot be discerned anymore in the dielectric spectra when the rate of underlying thermally activated processes exceeds certain characteristic frequency of the system.

Type
Research Letters
Copyright
Copyright © Materials Research Society 2013

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