Low-Temperature Phase Transformations in Weakly Doped Quantum Paraelectrics: Novel Features and Quantum Reentrant Dipolar Glass State in KTa0.982Nb0.018O3
- Institute of Physics, Czech Republic
- Rostov State University, Russia
- Universita di Pavia, Italy
- University of Osnabruck, Osnabruck, Germany
- ORNL
An unusual sequence of phase transitions (PT) and reentrant dipole glass-like phase formation at low temperatures was found recently in KTaO{sub 3} weakly doped with Li and Nb (K{sub 0.9986}Li{sub 0.0014}Ta{sub 0.976}Nb{sub 0.024}O{sub 3}) [Phys. Rev. B 63 (2001) 172]. We report on detailed low frequency (100 Hz-1 MHz) permittivity and Raman light scattering studies of similar composition, but without Li admixture, KTa{sub 1-x}Nb{sub x}O{sub 3} with x = 0.018 (KTN1.8). The aim of the study is to answer the question if the reentrant dipole glass-like phase exists in KTN1.8 and what is the microscopic origin of this phase. A detailed study of the sharp low-temperature PT observed at T{sub C} {approx} 27 K revealed properties inherent to the reentrant glass-type state at lower temperatures. The substitution of Nb for Ta influences the TO{sub 1} soft lattice mode and leads to PT with the long-range ferroelectric ordering. A crossover to an order-disorder polar microregion dynamics with a non-standard {var_epsilon}(T) behaviour and dipole glass-like formation were found below T{sub C} (at {approx}15 K), which is attributed to the randomness of the Nb distribution. A crossover to the long-range order was found under a dc bias field.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1003432
- Journal Information:
- Journal of Physics and Chemistry of Solids, Vol. 65, Issue 7; ISSN 0022-3697
- Country of Publication:
- United States
- Language:
- English
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