Dielectric Constant in Perovskite Type Crystals

Barrett, J.H.

doi:10.1103/physrev.86.118

Cited by 592 publications

(336 citation statements)

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“…Instead, it is closer to the shape predicted by Barrett's theory (Fig. S2) (30), indicating that the enhanced magnetic fluctuation in close vicinity to the spin-flop T * can be also linked to the enhanced lattice fluctuation with quantum mechanical population of the relevant phonon mode. This link might be a natural consequence of the existence of dynamic coupling between magnetism and lattice, called as electromagnon (31), in this multiferroic system.…”

Section: Physicsmentioning

confidence: 77%

Observation of a multiferroic critical end point

Kim

Haam

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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The study of abrupt increases in magnetization with magnetic field known as metamagnetic transitions has opened a rich vein of new physics in itinerant electron systems, including the discovery of quantum critical end points with a marked propensity to develop new kinds of order. However, the electric analogue of the metamagnetic critical end point, a "metaelectric" critical end point, has been rarely studied. Multiferroic materials wherein magnetism and ferroelectricity are cross-coupled are ideal candidates for the exploration of this novel possibility using magnetic-field (H) as a tuning parameter. Herein, we report the discovery of a magnetic-fieldinduced metaelectric transition in multiferroic BiMn 2 O 5 , in which the electric polarization (P) switches polarity along with a concomitant Mn spin-flop transition at a critical magnetic field H c . The simultaneous metaelectric and spin-flop transitions become sharper upon cooling but remain a continuous cross-over even down to 0.5 K. Near the P = 0 line realized at μ 0 H c ≈18 T below 20 K, the dielectric constant (ε) increases significantly over wide field and temperature (T ) ranges. Furthermore, a characteristic powerlaw behavior is found in the P(H) and ε(H) curves at T = 0.66 K. These findings indicate that a magnetic-field-induced metaelectric critical end point is realized in BiMn 2 O 5 near zero temperature. T he term "critical end point" refers to a singular point in the phase diagram of matter at the end of a first order phase line, as for example, the liquid-gas critical point of water. The importance of this special point for broad classes of matter has rapidly increased in recent years (1, 2). Not only can it provide large thermal fluctuations as a necessary ingredient for displaying universal power-law of physical quantities, but in the special case where the phase transition is suppressed to zero temperature, it can give rise to intense quantum mechanical fluctuations with a marked propensity to develop instabilities into new kinds of ground state. The latter case has been recently realized in itinerant metamagnets such as Sr 3 Ru 2 O 7 (3) and URu 2 Si 2 (4). These developments motivate a parallel search for a metaelectric critical end point. By analogy with magnetism, one might expect sudden cross-overs in electric polarization in the vicinity of a metaelectric critical endpoint to be a rather general phenomenon in (anti)ferroelectric materials under application of an electric field (E). However, to date, such metaelectric transitions induced by electric fields have been limitedly observed in specific systems such as relaxor ferroelectrics (5) and DyVO 4 with the Jahn-Teller structural distortion (6). One possible reason for the scarcity of the phenomenon is the practical difficulty of applying the large voltages required ( 1 kV) without inducing electrical breakdown. Magnetic fields may in fact be better candidates for inducing metaelectric transitions, because they not only avoid the problem of electrical breakdown but also provide a reversi...

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Section: Physicsmentioning

confidence: 77%

Observation of a multiferroic critical end point

Kim

Haam

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…13 , because it was very small in comparison to huge low-temperature ε' in SrTiO 3 and KTaO 3 ). Our use of the the Barrett formula in Eq.…”

Section: Resultsmentioning

confidence: 99%

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

Kamba¹,

Денисов²,

Veljko³

et al. 2007

Phys. Rev. B

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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.

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“…Recently, a single particle susceptibility has been reinvestigated by using quantum mechanics [6,7] to discuss the pressure-temperature phase diagram of KH 2 PO 4 [8], which is famous for a proton tunneling [9]. The Barrett equation [10] has been derived for the static susceptibility, and the pressure dependence of the transition line was calculated [7]. However, the single particle states were obtained by numerical solutions for the…”

Section: Introductionmentioning

confidence: 99%