Soft Mode Dynamics above and below the Burns Temperature in the Relaxor <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Pb</mi><mo>(</mo><mrow><msub><mrow><mi>Mg</mi></mrow><mrow><mn>1</mn><mi>/</mi><mn>3</mn></mrow></msub></mrow><mrow><msub><mrow><mi>Nb</mi></mrow><mrow><mn>2</mn><mi>/</mi><mn>3</mn></mrow></msub></mrow><mo>)</mo><mrow><msub><mrow><mi>O</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></math></span>

P. M. Gehring; S. Wakimoto; Z.-G. Ye; G. Shirane

doi:10.1103/PhysRevLett.87.277601

Soft Mode Dynamics above and below the Burns Temperature in the Relaxor $Pb ({Mg}_{1 / 3} {Nb}_{2 / 3}) O_{3}$

P. M. Gehring, S. Wakimoto, Z.-G. Ye, and G. Shirane

Phys. Rev. Lett. 87, 277601 – Published 11 December 2001

Abstract

We report neutron inelastic scattering measurements of the lowest-energy transverse optic (TO) phonon branch in the relaxor $Pb ({Mg}_{1 / 3} {Nb}_{2 / 3}) O_{3}$ from 400 to 1100 K. Far above the Burns temperature $T_{d} \sim 620 K$ we observe well-defined propagating TO modes at all wave vectors $q$ , and a zone center TO mode that softens in a manner consistent with that of a ferroelectric soft mode. Below $T_{d}$ the zone center TO mode is overdamped. This damping extends up to, but not above, the waterfall wave vector $q_{wf}$ , which is a measure of the average size of the polar nanoregions.

Received 21 August 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.277601

Authors & Affiliations

P. M. Gehring¹, S. Wakimoto^2,3, Z.-G. Ye⁴, and G. Shirane³

¹NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899
²Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7
³Physics Department, Brookhaven National Laboratory, Upton, New York 11973
⁴Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6