6533b82dfe1ef96bd1291407

RESEARCH PRODUCT

Quantum paraelectric behavior of pyrochlore PMN

S. KambaD. NuzhnyyS. DenisovS. VeljkoV. BovtunM. SavinovJ. PetzeltM. KalnbergaA. Sternberg

subject

Condensed Matter::Materials ScienceCondensed Matter - Materials ScienceMaterials Science (cond-mat.mtrl-sci)FOS: Physical sciencesPhysics::Optics

description

Pb_1.83Mg_0.29Nb_1.71O_6.39 (PMN) crystallizing in a cubic pyrochlore structure exhibits, as the first dielectrics with pyrochlore structure, typical feature of quantum paraelectrics - its permittivity continuously increases on cooling and levels off below ~ 30K, without any signature of a structural phase transition. Broad-band dielectric spectra do not show any dielectric dispersion in the real part of permittivity up to 8.8 GHz. THz and infrared spectra reveal a soft polar optic mode which is responsible for the temperature dependence of the permittivity. The leveling-off of the permittivity at low temperatures obeys the Barrett formula and the fitted vibrational zero-point energy 1/(2*k_B*T_1) corresponds to the measured soft mode frequency. The number of observed infrared phonons exceeds that predicted from the factor-group analysis which indicates that the structure is at least locally non-cubic.

yearjournalcountryeditionlanguage
2007-03-06
10.1103/physrevb.76.054125http://arxiv.org/abs/cond-mat/0703159