Phase Transition of the Uniaxial Disordered Ferroelectric Sr$_{0.61}$Ba$_{0.39}$Nb$_2$O$_6$

S. N. Gvasaliya; R. A. Cowley; L. I. Ivleva; S. G. Lushnikov; B. Roessli; A. Zheludev

paper

Phase Transition of the Uniaxial Disordered Ferroelectric Sr $_{0.61}$ Ba $_{0.39}$ Nb $_{2}$ O $_{6}$

arXiv:1206.2012

Abstract

We report a neutron scattering study of a ferroelectric phase transition in Sr $_{0.61}$ Ba $_{0.39}$ Nb $_{2}$ O $_{6}$ (SBN-61). The ferroelectric polarization is along the crystallographic $c$ -axis but the transverse acoustic branch propagating along the $<$ 1, 1, 0 $>$ direction does not show any anomaly associated with the this transition. We find no evidence for a soft transverse optic phonon. We do, however, observe elastic diffuse scattering. The intensity of this scattering increases as the sample is cooled from a temperature well above the phase transition. The susceptibility associated with this diffuse scattering follows well the anomaly of the dielectric permittivity of SBN-61. Below T $_{c}$ the shape of this scattering is consistent with the scattering expected from ferroelectric domain walls. Our results suggest that despite apparent chemical disorder SBN-61 behaves as a classic order-disorder uniaxial ferroelectric with critical fluctuations in the range $< 1 0^{- 11}$ s.

Phase Transition of the Uniaxial Disordered Ferroelectric Sr0.61​Ba0.39​Nb2​O6​

Abstract

Phase Transition of the Uniaxial Disordered Ferroelectric Sr $_{0.61}$ Ba $_{0.39}$ Nb $_{2}$ O $_{6}$