Quantum paraelectric behavior of pyrochlorePb1.83Mg0.29Nb1.71O6.39

Abstract

Pb1.83Mg0.29Nb1.71O6.39 (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 ∼ 30 K 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 kBT1 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.

Multiferroic Properties and Magnetoelectric Coupling of Fe‐Doped (Ba0.7Ca0.3)TiO3‐Ba(Zr0.2Ti0.8)O3 Ceramics

“…For the samples with x = 0.40, the dielectric constant increases with decreasing temperature and remains almost constant below 50 K, which is similar to the quantum paraelectric behavior of SrTiO 3 , where the long‐range ferroelectric order is suppressed by quantum fluctuations . The temperature‐dependent dielectric constant of quantum paraelectrics can be described by the Barrett formulawhere C is the Curie constant, T 1 represents the starting temperature of quantum fluctuations, and T 0 is the paraelectric Curie temperature. As shown in the inset of Figure f, of the samples with x = 0.40 is well fitted by Equation .…”

Recent Advances in Processing, Structural and Dielectric Properties of PMN-PT Ferroelectric Ceramics at Compositions Around the MPB

“…et al, 1983). Although A 2 B 2 O 7 compounds exhibit a wide variety of interesting physical properties, in high-performance ferroelectrics such as PMN-PT these compounds should be Recent Advances in Processing, Structural and Dielectric Properties of PMN-PT Ferroelectric Ceramics at Compositions Around the MPB 45 avoided due to their paraelectric characteristic (Kamba et al, 2007). The compound Pb 1.83 Mg 0.29 Nb 1.71 O 6.39 (PMN) exhibits a pyrochlore structure (space group Fd3m), frequently growing in the perovskite PMN ceramics, where the dielectric constant was found to increase as the temperature decreased, presenting an anomalous peak near 20 K, attributed to relaxation phenomena (Shrout & Swartz, 1983).…”

Magnetic resonance study of bulk and thin film EuTiO3

“…EuTiO3 is an incipient ferroelectric like SrTiO3 because its permittivity increases on cooling and saturates below ~20 K due to the softening of a phonon as the temperature is lowered in combination with the quantum fluctuations that occur at low temperature [1,2]. If a magnetic field is applied below TN, the soft mode frequency lowers further, causing permittivity to increase [3]. The room-temperature crystal structure of EuTiO3 is cubic (space group Pm3 ̅ m) [4], but near 280 K an antiferrodistortive phase transition to the tetragonal I4/mcm structure occurs [5][6][7][8].…”

“…Nowadays there are numerous studies on EuTiO3 in the form of bulk ceramics, single crystals, and thin films grown on different substrates (see e.g., [1][2][3][4][5][6][7][8]). In particular, ceramic samples of EuTiO3 have been studied by the electron paramagnetic resonance (EPR) technique down to about 50 K [12].…”