title: Phase transition of the uniaxial disordered ferroelectric Sr(0.61)Ba(0.39)Nb(2)O(6).
abstract: We report a neutron scattering study of a ferroelectric phase transition in Sr0.61Ba0.39Nb2O6 (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 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 the anomaly of the dielectric permittivity of SBN-61 well. Below Tc 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 <10(-11) s.
authors.affiliation: Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland.
authors.forename: S N
authors.initials: SN
authors.lastname: Gvasaliya
authors.forename: R A
authors.initials: RA
authors.lastname: Cowley
authors.forename: L I
authors.initials: LI
authors.lastname: Ivleva
authors.forename: S G
authors.initials: SG
authors.lastname: Lushnikov
authors.forename: B
authors.initials: B
authors.lastname: Roessli
authors.forename: A
authors.initials: A
authors.lastname: Zheludev
mesh_terms: D017609:Barium Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004560:Electricity; D033363:Neutron Diffraction; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D044367:Phase Transition; D013324:Strontium / Q000737:chemistry*; D013696:Temperature
chemical_list: D017609:Barium Compounds; D010087:Oxides; D009556:Niobium; D013324:Strontium