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DF: Fachverband Dielektrische Festkörper
DF 2: Nonlinear dielectrics, phase transitions, relaxors
DF 2.1: Talk
Monday, March 14, 2011, 11:00–11:20, KÖN Farb
Pressure induced Griffiths-like phase in Sn2P2S6 ferroelectrics with three-well potential — •Konstantin Z. Rushchanskii1, M. Kempa2, P. Ondrejkovic2, J. Hlinka2, P. Saint-Grégoire3, Ph. Bourges4, and Yu. M. Vysochanskii5 — 1Peter Grünberg Institut, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany — 2Institute of Physics AVCR, Prague, Czech Republic — 3University de Nimes, Nimes, France — 4Laboratoire Leon Brillouin, Saclay, France — 5Uzhgorod National University, Uzhgorod, Ukraine
The origin of the second-order phase transition in uniaxial Sn2P2S6 (SPS) monoclinic ferroelectrics is the relaxation of a lone-pair electron localized on Sn2+ cations, which results in nonlinear interaction of the soft polar and fully symmetrical optic modes and leads to a three-well potential in corresponding energy surface [1]. It is known [2] that systems with three-well potential, which are described by two order parameters (dipolar and quadrupolar), present a variety of stable, unstable and metastable phases at different temperatures. Combining ab initio derived effective Hamiltonian with Monte Carlo statistical simulations on large supercells, we first predict and then confirm experimentally by neutron diffuse scattering an existence of a pressure induced Griffiths-like phase in the PT-diagram near 0.6 GPa. KZR gratefully acknowledge the support from HGF Nachwuchsgruppe Programme VH-NG-409. [1] K.Z. Rushchanskii et al, Phys. Rev. Lett. 99, 207601 (2007); [2] C. Ekiz et al, Physica A 293, 215 (2001).