Anisotropic dielectric function in polar nano-regions of relaxor ferroelectrics

The paper suggests to treat the infrared reflectivity spectra of single crystal perovskite relaxors as fine-grained ferroelectric ceramics: locally frozen polarization makes the dielectric function strongly anisotropic in the phonon frequency range and the random orientation of the polarization at n...

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Bibliographic Details
Published inarXiv.org
Main Authors Hlinka, J, Ostapchuk, T, Noujni, D, Kamba, S, Petzelt, J
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 11.10.2005
Subjects
Anisotropy
Depolarization
Dielectric relaxation
Dielectric strength
Effective medium theory
Ferroelectric materials
Ferroelectricity
Frequency ranges
Harmonic oscillators
Infrared spectra
Inhomogeneity
Perovskites
Polarization
Reflectance
Relaxors
Single crystals
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Summary:The paper suggests to treat the infrared reflectivity spectra of single crystal perovskite relaxors as fine-grained ferroelectric ceramics: locally frozen polarization makes the dielectric function strongly anisotropic in the phonon frequency range and the random orientation of the polarization at nano-scopic scale requires to take into account the inhomogeneous depolarization field. Employing a simple effective medium approximation (Bruggeman symmetrical formula) to dielectric function describing the polar optic modes as damped harmonic oscillators turns out to be sufficient for reproducing all principal features of room temperature reflectivity of PMN. One of the reflectivity bands is identified as a geometrical resonance entirely related to the nanoscale polarization inhomogeneity. The approach provides a general guide for systematic determination of the polar mode frequencies split by the inhomogeneous polarization at nanometer scale.
ISSN:2331-8422
DOI:10.48550/arxiv.0510273