Phonon Localization Drives Polar Nanoregions in a Relaxor Ferroelectric

Published

April 10, 2014

Author(s)

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

Abstract

Relaxor Ferroelectrics¹, which are utilized as actuators and sensors^2-4, 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, T_d] 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 T_d, remains localized as PNRs form, and then delocalizes as PNRs grow. Although similar to intrinsic local modes (ILMs)^6-7 proposed to explain PNRs^8-10, 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.

Citation

Nature Communications

Volume

5

Pub Type

Journals

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Keywords

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

Citation

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], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=914605 (Accessed September 19, 2024)