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VOLUME 80 | ISSUE 5 | PAGE 403
Dynamics of cubic-tetragonal phase transition in KNbO3 perovskite
S. N. Gvasaliya^{+\square}, B. Roessli+, R. A. Cowley*, S. G. Lushnikov^{\square}, A. Choubey^{\nabla}, P. Günter^{\nabla}

+Laboratory for Neutron Scattering ETHZ & Paul Scherrer Institut CH-5232 Villigen PSI Switzerland *Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, UK ^\squareIoffe Physical Technical Institute, 194021, St. Petersburg, Russia ^{\nabla}Nonlinear Optics Laboratory, ETH Honggerberg, CH-8093 Zürich Switzerland


PACS: 61.12.-q, 63.50.+x, 64.60.-i, 77.80.-e
Abstract
The low-energy part of the vibration spectrum in KNbO3 was studied by cold neutron inelastic scattering in the cubic phase. In addition to acoustic phonons, we observe strong diffuse scattering, which consists of two components. The first one is quasi-static and has a temperature-independent intensity. The second component appears as quasi-elastic scattering in the neutron spectrum indicating a dynamic origin. From analysis of the inelastic data we conclude that the quasi-elastic component and the acoustic phonon are mutually coupled. The susceptibility associated with the quasi-elastic component grows as the temperature approaches TC.


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