Antiferroelectric Coupling Research Articles

Realization of sextuple polarization states and interstate switching in antiferroelectric CuInP2S6

Realization of higher-order multistates with mutual interstate switching in ferroelectric materials is a perpetual drive for high-density storage devices and beyond-Moore technologies. Here we demonstrate experimentally that antiferroelectric van der Waals CuInP2S6 films can be controllably stabilized into double, quadruple, and sextuple polarization states, and a system harboring polarization order of six is also reversibly tunable into order of four or two. Furthermore, for a given polarization order, mutual interstate switching can be achieved via moderate electric field modulation. First-principles studies of CuInP2S6 multilayers help to reveal that the double, quadruple, and sextuple states are attributable to the existence of respective single, double, and triple ferroelectric domains with antiferroelectric interdomain coupling and Cu ion migration. These findings offer appealing platforms for developing multistate ferroelectric devices, while the underlining mechanism is transformative to other non-volatile material systems.

Correlation between pyroelectric property and dielectric constant of antiferroelectrics

Theoretic results of dielectric constant, pyroelectric coefficient, and their correlation in the temperature range from antiferroelectric phase to paraelectric phase are derived in antiferroelectrics by introducing an antiferroelectric coupling coefficient and a ferroelectric coupling coefficient within Gibbs free energy framework. Numerical simulation on dielectric constant demonstrates a double-peak effect induced by applied electric field, which is coincident with the experimental results of thin films. The simulated temperature spectrum of pyroelectric coefficient shows a peak region around Curie temperature stretching like a sector shape. Correlation between dielectric constant and pyroelectric coefficient exhibits that sharp peak of dielectric constant corresponds to strong pyroelectric effect on wide temperature and electric field plane.

Full Antiferroelectric Performance and GMR Effect in Multiferroic La0.75Ba0.25Fe12O19 Ceramic

The potential application of multiferroic materials in new electronic devices attracts more and more attention from people either in an academic field or industry. This paper reports that M-type lanthanum-doped barium ferrite (La0.75Ba0.25Fe12O19) demonstrates full antiferroelectric (AFE) and excellent magnetoelectric coupling effects at room temperature, while its AFE phase displays a zero macroscopic net polarization. The dramatic change in the dielectric constant near the Curie temperature far below room temperature represents the transition from ferroelectrics (FE) to antiferroelectrics. The fully separated double electric polarization hysteresis (P–E) loops confirmed its AFE performance. Its EF and EA are located at 1100 kV/cm and 850 kV/cm, respectively. The large M–H loop showed a strong magnetic property simultaneously. The UV-Vis-NIR optical spectrum revealed that La0.75Ba0.25Fe12O19 is also a semiconductor, whose direct bandgap energy (Eg) was determined to be 1.753 eV. Meanwhile, La0.75Ba0.25Fe12O19 showed strong ME coupling and a GMR effect. A 1.1 T magnetic field reduced its resistance by 110% at 30 kHz. The multiple functions combined in one phase would create new options for high energy storage capacitors, microactuators, pyroelectric safety sensors, cooling devices, and pulsed power generators and so on, as well as great opportunities for generating new electronic devices with active magnetoelectric coupling effects.

Dynamic antiferroelectric behavior of dielectric susceptibility of a ferroelectric heterostructure

The dynamic antiferroelectric behavior of dielectric susceptibility of a ferroelectric heterostructure (FEH) containing two different ferroelectric (FE) films with an antiferroelectric interfacial coupling between them has been investigated by means of a modified Landau theory appended Landau-Khalatnikov (L-K) equation. Two identical surface transition layers (STLs) within each film and a parameter β described discrepancies of physical properties enter two component films are considered, which is a more realistic model. Due to the competitive action of antiferroelectric coupling, STL, β and frequency of electric field, the dielectric susceptibility of system may present four or two peaks, exhibiting an antiferroelectriclike behavior or a ferroelectric behavior, respectively. We can obtain the characteristics of dielectric susceptibility for our need through appropriate option of these parameters.

Ferroelectric and antiferroelectric distortions coupling of nitride perovskite LaWN3 under epitaxial strain using first-principles calculations

LaWN3, a novel nitride perovskite, have been synthesized and its piezoelectric properties have been investigated (Talley K. R. et al., Science, 374 (2021) 1488). However, the understanding of its ferroelectric properties under the external strain is still lacking. Here, the misfit-strain–dependent coupling between antiferrodistortions (AFD) and ferroelectric (FE) distortions has been studied by using a first-principle approach. It can be observed that AFD and FE distortions can work cooperatively with each other as the compressive strain increases, and the coupling energy between them is found to work in different ways under various strains. Our results show that the coupling tends to stabilize the ground structure when the compressive strain is smaller than −1.9%, it works oppositely when the compressive strain becomes larger than 1.9%. Our results can provide us with more hints about the influence of the epitaxial strains on the intrinsic coupling behavior in the perovskite ferroelectric compounds, which is very important for us to design and fabricate new kinds of functional materials.

Quasi‐1D Antiferroelectricity in Centrosymmetric CsTaS3 Crystal

Abstract1D ferroelectric (FE) materials are expected to be promising low‐dimensional materials for nanometer devices, but are rarely reported. The previous experiment discovered that quasi‐1D CsTaS3 crystalizes in centrosymmetric space group, but in which the Ta cations have a strange shift along the c axis from the center of TaS6 octahedron. Here, the crystal structure, electronic structure, ferroelectric, and piezoelectric properties of CsTaS3 by using first‐principles calculations are studied. It is found that the empty d orbitals of Ta cations induce the distortions of TaS6 octahedra, which bring the polarity along a given [TaS3]− chain. The adjacent chains are antiferroelectric (AFE) coupling making CsTaS3 being an AFE material. However, the FE phase of CsTaS3 is supposed to be accessible since its total energy is only 0.3 meV per formula higher than that of the AFE phase. The polarization of FE CsTaS3 is estimated to be 16.8 μC cm−2, which is comparable to those of well‐known FE perovskites. The work predicts a quasi‐1D AFE material, which would be helpful for subsequent experimental work.

Stacking-Dependent Interlayer Ferroelectric Coupling and Moiré Domains in a Twisted AgBiP2Se6 Bilayer.

Rotation/twisting of bilayers could induce unprecedented new physics due to stacking-dependent electronic properties and interlayer coupling, such as the superconductivity in twisted bilayer graphene, which can find applications in electronics. However, deep understanding at the atomic/electronic levels is limited by the capability of accurate theoretical simulations. Here, from first-principles simulations, we found that the AgBiP2Se6 bilayer has stacking-dependent ferroelectric ground states due to interlayer polarization coupling. Interlayer ferroelectric coupling is preferred in an AA-stacked AgBiP2Se6 bilayer, but antiferroelectric coupling is preferred in AB- or AC-stacked configurations. The ferroelectric Moiré patterns are thus observed in a twisted AgBiP2Se6 bilayer with ferroelectric (antiferroelectric) interlayer couplings in the AA (AB/AC)-stacked areas. Our work for the first time unveils the effects of twisting/rotation on interlayer polarization coupling and provides a real example of ferroelectric Moiré patterns.

A study on the mechanism of switching dynamic of ferroelectric bilayers by using Landau theory

We consider a bulk system of ferroelectric bilayer with an antiferroelectric interface coupling between two similar materials which have second-order phase transitions. Landau theory and Landau–Khalatnikov equation are used to study the dynamic switching phenomenon of this ferroelectric bilayers under a step electric field. A bilinear coupling that achieved a symmetry condition is taken into account in the Landau free-energy expression. We found that switching time is decreased for the system of weak antiferroelectric interface coupling, as well as for the system when the thickness ratio between the two layers is large. It is shown here by dynamic switching that the polarization reversal occurs in one step in the contrary to the static dielectric hysteresis loop. Negative and positive peaks of switching current is discussed.

Tuning the temperature-induced local-dipole coupling in (1−x)Na0.5Bi0.5TiO3-xBaTiO3 via electric field

In situ temperature-dependent Raman-scattering experiments under an external dc electric field E have been performed on (1−x)Na0.5Bi0.5TiO3-xBaTiO3 single crystals with x ranging from 0.013 to 0.074 in order to gain further insights into the atomistic mechanism of polar coupling in lead-free perovskite-type (ABO3) ferroelectric solid solutions near the morphotropic phase boundary (MPB). The polarized Raman spectra collected between 770 and 100 K under an E applied along the pseudocubic [100] direction were analyzed in terms of hard-mode spectroscopy. The results reveal enhanced coupling between the polar displacements of the A-site Bi3+ and B-site Ti4+ cations for x=0.048∼xMPB when a moderate E[100] field is applied, a local-scale phenomenon that might be responsible for the known drift of the MPB under external stimuli. In addition, for all studied compounds, the characteristic temperatures TA−A′ and TA−A′′, preceding the macroscopic Tm and Td and related to mesoscopic-scale antiferroelectric and ferroelectric coupling processes within the A-site-cation subsystem in a zero field, merge into one even under a weak electric field, suggesting that the structural state between the paraelectric and ferroelectric zones in the x-T diagram is weak ferrielectric.

Mechanism of double-loop and double-dielectric-peak in antiferroelectrics

Antiferroelectric double loops and double dielectric peaks occurred at an electric field circle synchronously are confirmed theretically by solving the kittel’s function with the idea of different responses of dipoles to applied electric field (E) in E-direction and anti-E-direction in antiferroelectrics. By solving problem of inversion of dipoles to ferroelectric phase controlled by thermodynamic parameters and the antiferroelectric coupling coefficient in antiferroelectric phase, the numerically simulated results exhibit that antiferroelectric phase can transform to ferroelectric phase with two approaches: decrease in temperature to a critical temperature, and increase in parameter α0. The results are well coincident with experimental results.

Charge transport in a polar metal

The fate of electric dipoles inside a Fermi sea is an old issue, yet poorly explored. Sr{}_{1-x}Ca{}_{x}TiO{}_{3} hosts a robust but dilute ferroelectricity in a narrow (0.0018 < x < 0.02) window of substitution. This insulator becomes metallic by removal of a tiny fraction of its oxygen atoms. Here, we present a detailed study of low-temperature charge transport in Sr{}_{1-x}Ca{}_{x}TiO{}_{3-delta }, documenting the evolution of resistivity with increasing carrier concentration (n). Below a threshold carrier concentration, {n}^{* }(x), the polar structural-phase transition has a clear signature in resistivity and Ca substitution significantly reduces the 2 K mobility at a given carrier density. For three different Ca concentrations, we find that the phase transition fades away when one mobile electron is introduced for about 7.9pm 0.6 dipoles. This threshold corresponds to the expected peak in anti-ferroelectric coupling mediated by a diplolar counterpart of Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction. Our results imply that the transition is driven by dipole–dipole interaction, even in presence of a dilute Fermi sea. Charge transport for n < {n}^{* }(x) shows a non-monotonic temperature dependence, most probably caused by scattering off the transverse optical phonon mode. A quantitative explanation of charge transport in this polar metal remains a challenge to theory. For nge {n}^{* }(x), resistivity follows a T-square behavior together with slight upturns (in both Ca-free and Ca-substituted samples). The latter are reminiscent of Kondo effect and most probably due to oxygen vacancies.

Dynamic hysteresis loop in a ferroelectric heterostructure

A Landau–Devonshire theory in combination with Landau–Khalatnikov dynamic equation has been firstly used to study the dynamic hysteresis loop of a ferroelectric heterostructure consisting of two different films. The surface transition layer within each component film and an antiferroelectric coupling at the interface between two films are considered. A parameter β is introduced to describe the differences of physical properties between two constituent films. The influence of parameterβ, surface transition layer, antiferroelectric coupling and electric field frequency on the dynamic hysteresis loop of the ferroelectric heterostructure is discussed in detail. The results show that the system can exhibit antiferroelectriclike behavior (i.e., multi-loop hysteresis) through tuning some critical factors.

Structural transformations in (1−x)Na0.5Bi0.5TiO3−xBaTiO3 single crystals studied by Raman spectroscopy

Hard-mode Raman spectroscopy was applied to analyze the temperature-induced transformation processes in perovskite-type $({\mathrm{ABO}}_{3})$ single crystals of $(1\text{\ensuremath{-}}x){\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{0.5}{\mathrm{TiO}}_{3}\text{\ensuremath{-}}x{\mathrm{BaTiO}}_{3}$ (NBT-$x\mathrm{BT})$ in a wide temperature range between 100 and 1010 K and a composition range of $x=0--0.074$ across the morphotropic phase boundary (MPB). The results show abundant uncoupled ferroic structural distortions even at 1010 K and coexistence of two types of mesoscopic-scale ferroic order at lower temperatures. Octahedral ${\mathrm{BO}}_{6}$ tilting is typical of pure NBT, while the incorporation of A-site ${\mathrm{Ba}}^{2+}$ suppresses the tilting and promotes the off centering of ${\mathrm{BO}}_{6}$ octahedra. The temperature evolution of the phonon modes clearly reveals the two macroscopically observed critical temperatures ${T}_{m}$ and ${T}_{d}$ as well as, in the case of $x\ensuremath{\ne}0$, two characteristic temperatures ${T}^{\ensuremath{'}}$ and ${T}^{\ensuremath{'}\ensuremath{'}}$ preceding the ${T}_{m}$ and ${T}_{d}$, respectively, which are attributed to mesoscopic-scale antiferroelectric and ferroelectric coupling processes within the A-site-cation subsystem. At $x\phantom{\rule{4pt}{0ex}}l\phantom{\rule{4pt}{0ex}}{x}_{\mathrm{MPB}}$ the two sublattices, off-centered A-site cations and off-centered B-site cations, remain incoherent in the entire temperature range. Only when the amount of Ba reaches ${x}_{\mathrm{MPB}}$ the two subsystems couple dynamically, which can explain the enhancement of properties at the MPB. The overall ferroic distortion, however, has a minimum at the MPB, probably because at ${x}_{\mathrm{MPB}}$ the ferroelectric coupling between B-site ${\mathrm{Ti}}^{4+}$ cations is reduced to a greater extent than the enhancement of ferroelectric coupling between A-site ${\mathrm{Bi}}^{3+}$ cations.

Monte Carlo simulation of dielectric properties of a mixed spin-3/2 and spin-5/2 Ising ferrielectric nanowires

ABSTRACTDielectric properties of Ising ferrielectric nanowires with spin-3/2 core and spin-5/2 shell structure are systematically studied by the use of the Monte Carlo simulation in the presence of the external longitudinal electric field. Special focus is given to the effects of the core and shell interactions, the interface coupling and the temperature on the core and shell polarizations, the specific heat, the compensations points, the susceptibility and hysteresis behaviors. Some characteristic behaviors are found, such as the existence of triple hysteresis loops for appropriate values of the system parameters affected by the antiferroelectric interface coupling constant and the temperature. The results are compared with those of recently published works and a qualitatively good agreement is found.

Continuous carbon fiber polymer–matrix composites in unprecedented antiferroelectric coupling providing exceptionally high through-thickness electric permittivity

Continuous carbon fiber polymer–matrix composites in unprecedented antiferroelectric coupling, as enabled by stacking composites with positive value (up to 400) and negative value (down to −600) of the electric permittivity, provide exceptionally high through-thickness permittivity up to 78,000 (≤2.0 MHz), corresponding to a capacitance of 370 μF/m2. The high capacitance is consistent with the equation for negative and positive capacitors in series. The permittivity tailoring of the composites involves dielectric cellulosic tissue paper interlaminar interlayers. Negative permittivity (not previously reported for carbon fiber composites) requires the paper to be wet with tap water (resistivity 1.5 kΩ cm) during incorporation in the composite, though the water evaporates and leaves ions at very low concentrations during composite fabrication, and also requires optimum through-thickness resistivity (e.g., 1 kΩ cm, as given by paper thickness 35 μm); it is probably due to interactions between the functional groups on the carbon fiber surface and the residual ions (mainly chloride) left after tap water evaporation.

Electric-field-induced local structural phenomena in Pb-based ABO3-type relaxor ferroelectrics.

Lead-based ABO3-type relaxors and related systems have numerous applications in modern technical devices because of their remarkably high dielectric permittivity and piezoelectric/electroelastic and electro-optic coefficients. However, lead is not desired from an environmental point of view, and to switch to alternative alkali-, Ba-, or Bi-based relaxor systems, one must understand in great detail the structural mesoscopic order and coupling processes responsible for the outstanding performance and multifunctionality of the exemplar Pb-based compounds. To elucidate the type of ferroic coupling, three relaxor compounds PbSc0.5Ta0.5O3 (PST), Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba), and PbSc0.5Nb0.5O3 (PSN), were studied by polarized Raman scattering and acoustic emission at different temperatures and under an external electric field. The results reveal the coexistence of mesoscopic-scale ferroelectric and antiferroelectric coupling, which are predominantly related to B-site cations and A-site Pb cations, respectively. This suggests that the polar structural state of relaxors is frustrated ferrielectric. The presence of A-site cations with affinity to off-center is significant for the development of mesoscopic-scale antiferroelectric order coexisting with the mesoscopic-scale ferroelectric order.

Electric-field-induced local structural phenomena in relaxor ferroelectric PbSc0.5Nb0.5O3 near the intermediate temperature T* studied by Raman spectroscopy

Raman spectroscopy at different temperatures and under an external electric field E was applied to PbSc0.5Nb0.5O3 single crystals in order to gain further insights into the mesoscopic-scale coupling processes in perovskite-type (ABO3) relaxor ferroelectrics. Parallel and cross-polarized Raman spectra were collected between 800–80 K with E applied along the cubic [1 0 0], [1 1 0] or [1 1 1] crystallographic directions. The analysis was focused on the field-induced changes in the temperature evolution of three low-energy phonon modes: the Pb-localized mode near 50 cm−1, the Pb-BO3 translation mode near 150 cm−1, and the B-cation-localized mode near 250 cm−1. The results show that competitive ferroelectric (FE) and antiferroelectric (AFE) coupling exists within the system of off-centred Pb2+ cations, within the system of off-centred B-site cations as well as between off-centred Pb2+ and B-site cations. The strong AFE-type coupling between Pb2+ cations along the cubic body diagonal significantly influences the coupling between the B-site cations via the Pb-BO3 mode and results in AFE-type behaviour of the ‘microscopic’ T* determined from the B-cation-localized mode near 250 cm−1, which explains the previously reported non-trivial field dependence of the ‘macroscopic’ characteristic temperatures: the temperature of the dielectric-permittivity maximum Tm, T*, and the Burns temperature TB. The comparative analysis between PbSc0.5Nb0.5O3 and PbSc0.5Ta0.5O3 indicates that two major displacive order parameters couple to form a relaxor state in B-site complex perovskites: the FE order associated with polar shifts of B-site cations and the AFE order associated with polar shifts of A-site cations. The latter penetrates through both polar and non-polar regions, but it is highly frustrated due to the high density of translation-symmetry faults in the chemical NaCl-type B-site order. The frustrated AFE order of off-centred A-site cations might be the key factor for the existence of a relaxor state.

Poling and Depoling Effects on Dielectric Properties and Domain Structures in Relaxor 24Pb(In1/2Nb1/2)O3–46Pb(Mg1/3Nb2/3)O3–30PbTiO3 near a Morphotropic Phase Boundary Composition

The temperature dependence of the complex relative permittivity in a relaxor ferroelectric solid solution 24Pb(In1/2Nb1/2)O3–46Pb(Mg1/3Nb2/3)O3–30PbTiO3 (PIN–PMN–PT) crystal poled and depoled was measured from room temperature to 200 °C at various frequencies. The poled sample exhibits transitions from the ferroelectric (FE) phase to the relaxor (RE) phase on heating, and after that, the depoled one exhibits those from the RE phase to the glassy freezing phase on cooling. An RE-type dielectric dispersion with a weak frequency (f) dependence was observed. Such a dielectric dispersion in the RE state was found to be based on tweed domain structures observed by polarization light microscopy (PLM) and piezoelectric force microscopy (PFM) due to the competition between the antiferroelectric (AFE) and FE coupling in the RE state. The temperature dependence of complex permittivity with resonance- and relaxor-type dielectric dispersions in the poled and depoled samples was characterized by hierarchical domain structures.

Size Effects of the Properties in a Ferroelectric Bilayer Film with Surface Transition Layers

Using the transverse Ising model theory, a ferroelectric bilayer film, considering the surface transition layer within each constituent slab and an interfacial coupling between two slabs, is investigated in the framework of the mean-field approximation. We discuss in detail the thickness effects of the spontaneous polarization and dielectric susceptibility of a ferroelectric bilayer film under two conditions of interfacial coupling: ferroelectric and antiferroelectric coupling. The results show some unexpected phenomena for a small thickness of a ferroelectric bilayer film.

Zero- and finite-temperature mean field study of magnetic field induced electric polarization in Ba2CoGe2O7: Effect of the antiferroelectric coupling

We investigate the spin induced polarization in the multiferroic compound Ba${}_{2}$CoGe${}_{2}$O${}_{7}$ using variational and finite-temperature mean field approaches, with the aim to reproduce the peculiar behavior of the induced polarization in a magnetic field observed experimentally in Murakawa et al. [Phys. Rev. Lett. 105, 137202 (2010)]. The compound is usually described by a spin-3/2 Heisenberg model extended with easy-plane anisotropy and Dzyaloshinskii-Moriya (DM) interaction. By applying a magnetic field parallel to the $[110]$ axis, three phases can be distinguished in this model: (i) At high magnetic field, we find a partially magnetized phase with spins parallel to the fields and uniform polarization. (ii) Below a critical field, the ground state is a twofold-degenerate canted antiferromagnet, where the degeneracy can be lifted by a finite DM interaction. (iii) At zero field, a U$(1)$ symmetry-breaking phase takes place, exhibiting a Goldstone mode. We find that extending the Hamiltonian with an antiferroelectric term results in the appearance of a canted ferrimagnetic phase for $h\ensuremath{\lesssim}1$ T. This phase is characterized by a finite staggered polarization, as well as by a magnetization closing a finite angle with the applied field leading to torque anomalies.