S. G. Lushnikov

Low-temperature transverse dielectric and pyroelectric anomalies of uniaxial tungsten bronze crystals

Low-temperature dielectric and pyroelectric properties were investigated for filled and unfilled tungsten bronze (TB) crystals, i.e., (Sr0.61Ba0.39)5Nb10O30, (K0.5Na0.5)1.0(Sr0.75Ba0.25)4.5Nb10O30, K5.80Li3.82Nb10.12O30, and K5.20Li2.34Nb10.88O30 with the spontaneous polarizations along the c axis at room temperature except for the last one. In all samples, transverse dielectric constant along the a axis showed a universal dielectric dispersion in the low-temperature range resembling a diffuse phase transition. Characteristic relaxation times obtained from the dielectric loss peaks followed the Arrhenius law, signifying thermal activation processes. The distribution of relaxation times seems to be caused by the distribution of activation energy, which has been successfully obtained by scaling the temperature- and frequency-dependent dielectric losses. This broadening may be attributed to the intrinsic randomness due to the charge disorder and quenched random fields caused by the unfilled structure and the...

Raman scattering in the relaxor-type ferroelectric Na1/2Bi1/2TiO3

Abstract A complex perovskite-type single crystal Na1/2Bi1/2TiO3 (NBT) with a cubic-tetragonal-trigonal sequence of phase transition, ending in a ferroelectric state, has been studied by Raman scattering. In additional to a possible soft mode which softens far below the phase transition, a broad central component has been revealed in a form which let us analyze the temperature dependence of its intensity. The central component has features of a relaxation mode with the highest intensity in the intertransirion region, so it arises from a critical light scattering on fluctuations of two coupled order parameters. The correlations between the central component behaviour, acoustic anomalies and dielectric response as well as their relation to a model with competing interactions are discussed. It is suggested that the broad central peak component in light scattering is characteristic of the relaxor-type ferroelectrics with a sequence of phase transformation irrespective of whether transitions are really observed as in NBT or whether transitions are frustrated at normal conditions as in PbMg1/3Nb2/3O3 (PMN).

Spin-glass state and long-range magnetic order in Pb ( Fe 1 / 2 Nb 1 / 2 ) O 3 seen via neutron scattering and muon spin rotation

We have investigated the magnetic ground state of the multiferroic relaxor ferroelectric

A central peak in light scattering from the relaxor-type ferroelectric Na1/2Bi1/2TiO3

\text{Pb}({\text{Fe}}_{1/2}{\text{Nb}}_{1/2}){\text{O}}_{3}

Glasslike state in PbFe1/2Nb1/2O3 single crystal

with

Different dynamic behaviors of Pb(Mg1/3Ta2/3)O3 and Ba(Mg1/3Ta2/3)O3 single crystals studied by micro-Brillouin scattering and dielectric spectroscopy

\ensuremath{\mu}\text{SR}

Quasi-Elastic Scattering, Random Fields and phonon-coupling effects in PbMg1/3Nb2/3O3

spectroscopy and neutron scattering. We find that a transition to a partially disordered phase occurs below

Disorder and relaxation mode in the lattice dynamics of PbMg

T=20\text{ }\text{K}

_{1/3}

that coexists with long-range antiferromagnetic ordering. The disordered phase resembles a spin glass. No clustering of magnetic ions could be evidenced by

Nb

\ensuremath{\mu}\text{SR}