Quantum paraelectric behavior of pyrochlore Pb{sub 1.83}Mg{sub 0.29}Nb{sub 1.71}O{sub 6.39}
- Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i. Na Slovance 2, 182 21 Prague 8 (Czech Republic)
Pb{sub 1.83}Mg{sub 0.29}Nb{sub 1.71}O{sub 6.39} crystallizing in a cubic pyrochlore structure exhibits a typical feature of quantum paraelectrics--its permittivity continuously increases on cooling and levels off below {approx}30 K without any signature of a structural phase transition. Broadband dielectric spectra do not show any dielectric dispersion in the real part of permittivity up to 8.8 GHz. Terahertz 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{sub B}T{sub 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 noncubic.
- OSTI ID:
- 21055100
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 76, Issue 5; Other Information: DOI: 10.1103/PhysRevB.76.054125; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COOLING
CRYSTAL STRUCTURE
DISPERSIONS
FERROELECTRIC MATERIALS
GHZ RANGE
INFRARED SPECTRA
LEAD COMPOUNDS
MAGNESIUM COMPOUNDS
NIOBIUM OXIDES
PERMITTIVITY
PHASE TRANSFORMATIONS
PHONONS
PYROCHLORE
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0065-0273 K