Eur. Phys. J. B 15, 615-623 (2000)
https://doi.org/10.1007/s100510051164

Low energy phonon spectrum and its parameterization in pure KTaO₃ below 80 K

¹ Laboratoire des VerresUMR 5587 CNRS, Université Montpellier 2, 34095 Montpellier, France
² Laboratoire de Céramique, EPFL, 1015 Lausanne, Switzerland
³ Institut Laue Langevin, BP. 156, 38042 Grenoble Cedex 9, France
⁴ Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6056, USA

Received: 29 September 1999
Revised: 6 January 2000
Published online: 15 June 2000

Abstract

High resolution data on low energy phonon branches (acoustic and soft optic) along the three principal symmetry axes in pure KTaO₃ were obtained by cold neutron inelastic scattering between 10 and 80 K. Additional off-principal axis measurements were performed to characterize the dispersion anisotropy (away from the and axes). The parameters of the phenomenological model proposed by Vaks [28] are refined in order to successfully describe the experimental low temperature (10 < T < 100 K) dispersion curves, over an appreciable reciprocal space volume around the zone center ( rlu). The refined model, which involves only 4 temperature-independent adjustable parameters, is intended to serve as a basis for quantitative computations of multiphonon processes.