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Mode-coupling and polar nanoregions in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3

S. Wakimoto·C. Stock·Z. -G. Ye·W. Chen·P. M. Gehring·G. Shirane
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Abstract

We present a quantitative analysis of the phonon lineshapes obtained by neutron inelastic scattering methods in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN). Differences in the shapes and apparent positions of the transverse acoustic (TA) and transverse optic (TO) phonon peaks measured in the (300) and (200) Brillouin zones at 690 K are well described by a simple model that couples the TA and soft TO modes in which the primary parameter is the wave vector and temperature-dependent TO linewidth Gamma(q,T). This mode-coupling picture provides a natural explanation for the uniform displacements of the polar nanoregions, discovered by Hirota et al., as the PNR result from the condensation of a soft TO mode that also contains a large acoustic component.

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S. Wakimoto, C. Stock, Z. -G. Ye, W. Chen, P. M. Gehring, G. Shirane. 2002-08-09. Mode-coupling and polar nanoregions in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3. https://doi.org/10.1103/physrevb.66.224102

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