Anomalous transverse acoustic phonon broadening in the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O_3

T. -Y. Koo; P. M. Gehring; G. Shirane; V. Kiryukhin; G. Lee; S. -W. Cheong

doi:10.1103/PhysRevB.65.144113

paper

Anomalous transverse acoustic phonon broadening in the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O_3

arXiv:cond-mat/0110531 · doi:10.1103/PhysRevB.65.144113

Abstract

The intrinsic linewidth $Γ_{T A}$ of the transverse acoustic (TA) phonon observed in the relaxor ferroelectric compound Pb(Mg $_{1/3}$ Nb $_{2/3})_{0.8}$ Ti $_{0.2}$ O $_{3}$ (PMN-20%PT) begins to broaden with decreasing temperature around 650 K, nearly 300 K above the ferroelectric transition temperature $T_{c}$ ( $\sim 360$ K). We speculate that this anomalous behavior is directly related to the condensation of polarized, nanometer-sized, regions at the Burns temperature $T_{d}$ . We also observe the ``waterfall'' anomaly previously seen in pure PMN, in which the transverse optic (TO) branch appears to drop precipitously into the TA branch at a finite momentum transfer $q_{w f} \sim 0.15$ Å $^{- 1}$ . The waterfall feature is seen even at temperatures above $T_{d}$ . This latter result suggests that the PNR exist as dynamic entities above $T_{d}$ .

6 pages, 4 figures

Anomalous transverse acoustic phonon broadening in the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O_3

Abstract

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