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Correspondence: Phantom Phonon Localization in Relaxors



Peter M. Gehring, Daniel E Parshall, Leland Weldon Harriger, Christopher Stock, Guangyong Xu, Xiaobing Li, Haosu Luo


Manley et al. (Ref. [1]) report the observation of an unexpected, weak, phonon mode located in energy between that of the transverse acoustic (TA) and soft transverse optic (TO) modes in the relaxor ferroelectric Pb[(Mg0.33Nb0.67)1-xTix]O3 (PMN-xPT) with Ti content x = 0.30. The energy of this extra mode varies little with wave vector in the cubic (paraelectric) phase, and this was interpreted as evidence of phonon localization. Any excitation that is localized in space must be extended in reciprocal space Q. To confirm this property, we performed a standard test on a PMN-xPT single crystal of nominally identical composition. Our data prove that the local mode (LM) is not localized in space but highly localized in Q. We show this by comparing the rates at which the intensities of the Bragg, elastic incoherent, TA phonon, and LM neutron scattering cross sections decrease as the cubic crystal [100] axis is gradually tilted out of the horizontal scattering plane. We can explain the LM quantitatively assuming only that it results from a spurious double scattering process involving a phonon and a Bragg reflection.
Nature Communications


Relaxors, phonon localization, double scattering, neutron scattering


, P. , , D. , , L. , Stock, C. , Xu, G. , Li, X. and Luo, H. (2017), Correspondence: Phantom Phonon Localization in Relaxors, Nature Communications, [online], (Accessed March 3, 2024)
Created December 5, 2017, Updated July 26, 2018