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Phonon Localization Drives Polar Nanoregions in a Relaxor Ferroelectric



M. E. Manley, Jeffrey W. Lynn, D. L. Abernathy, E. D. Specht, O. Delaire, A. R. Bishop, R. Sahul, J. D. Budai


Relaxor Ferroelectrics1, which are utilized as actuators and sensors2-4, exemplify a class of poorly understood functional materials where an interplay between disorder and phase instability results in nanostructure. Foremost, there is no definitive explanation for the onset of relaxor behavior [Burns temperature5, Td] or the origin of polar nanoregions [PNRs]. Here, using neutron scattering on relaxor [Pb[MgYd1/3}Nb2/3}]O3]0.69 [PbTiO3]0.31[PMN-31%PT] we find a new mode below the lowest transverse-optic [TO] phonon that localizes and sharpens on cooling to Td, remains localized as PNRs form, and then delocalizes as PNRs grow. Although similar to intrinsic local modes (ILMs)6-7 proposed to explain PNRs8-10, these modes differ in that they are resonant with the ferroelectic-TO phonon. Long-lived resonant ILMs are possible in patterns that trap the radiating phonons11, and single-wavelength trapped ferroelectric phonons are observed with a coherence length matching the PNRs. Nanoregions of standing ferroelectric phonons, trapped by disordered resonant ILMs via Anderson localization^12-14^, explain our observations and the PNRs, including their size, shape, spatial distribution, structure, and fluctuations. Since ILMs and Anderson localization are universal phenomena, we anticipate that this mechanism applies broadly in this class of materials.
Nature Communications


Relaxor Ferroelectric, polar nanoregions, phonon dynamics, inelastic neutron scattering, anharmonic interactions


Manley, M. , Lynn, J. , Abernathy, D. , Specht, E. , Delaire, O. , Bishop, A. , Sahul, R. and Budai, J. (2014), Phonon Localization Drives Polar Nanoregions in a Relaxor Ferroelectric, Nature Communications, [online], (Accessed April 18, 2024)
Created April 9, 2014, Updated October 12, 2021