Anisotropic dielectric function in polar nano-regions of relaxor ferroelectrics

Abstract

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.

arXiv comment5 pages, 2 figures

References in corpus (9)

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Cited by in corpus (7)

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• Absence of ferroelectricity in BiMnO3 ceramics
• Far infrared and terahertz spectroscopy of ferroelectric soft modes in thin films: A review
• Infrared, terahertz, and microwave spectroscopy of the soft and central modes in Pb(Mg1/3Nb2/3)O3
• Quantum paraelectric behavior of pyrochlore PMN
• Broadband dielectric spectroscopy of Ba(Zr,Ti)O3: dynamics of relaxors and diffuse ferroelectrics