Coexistence Of Ferroelectricity Research Articles

Room temperature multiferroic properties of single-phase (Bi0.9La0.1)FeO3–Ba(Fe0.5Nb0.5)O3 solid solution ceramics

The crystal structure and multiferroic properties of single-phase (Bi0.9La0.1)FeO3–Ba(Fe0.5Nb0.5)O3 ceramics were investigated. The rhombohedral-type structure of 1.0(Bi0.9La0.1)FeO3) was transformed to a monoclinic-type structure for the 0.5(Bi0.9La0.1)FeO3–0.5Ba(Fe0.5Nb0.5)O3) composition. It shows the coexistence of ferroelectricity and magnetism at room temperature, represented by a high dielectric constant with ferroelectric hysteresis and clear magnetic hysteresis behavior. The authors propose that the solid solution of A and B site cations according to their ionic radii and valence state stabilized the spontaneous polarization and magnetization at room temperature.

Electronic mechanism for the coexistence of ferroelectricity and ferromagnetism

We study the strong-coupling limit of a two-band Hubbard Hamiltonian that includes an interorbital on-site repulsive interaction ${U}_{ab}$. When the two bands have opposite parity and are quarter filled, we prove that the ground state is simultaneously ferromagnetic and ferroelectric for intraorbital Coulomb interactions ${U}_{aa},{U}_{bb}\ensuremath{\gg}{U}_{ab}$. We also show that this coexistence leads to an enormous magnetoelectric effect.

Coexistence of ferroelectricity and ferromagnetism in tantalum clusters

The atomic and electronic structures of Ta(N) (N=2-23) clusters have been determined in the framework of pseudopotential density-functional calculations, based upon an unbiased global search with guided simulated annealing to an empirical potential. It is found that the ground-state structures of Ta(N) are very similar to those of Nb(N), showing no preference for the icosahedral growth. Also, a size- and structure-dependent ferroelectricity is found in these tantalum clusters. More importantly, it is found that the ferroelectricity and ferromagnetism can coexist in the homogeneous transition-metal cluster, offering a possibility to obtain a new type of "multiferroic" materials composed of the clusters. Finally, the far-infrared spectroscopy is suggested to be an efficient tool to distinguish the ferroelectric clusters.

Synthesis and Properties of Multiferroic La‐Modified BiFeO3 Ceramics

Multiferroic Bi(1−x)LaxFeO3 was synthesized by a modified Pechini approach. Optimal conditions for the synthesis of single‐phase Bi(1−x)LaxFeO3 powder were reported. A conventional sintering process was used to fabricate Bi(1−x)LaxFeO3 ceramics. Ferroelectric and magnetic loops measured at room temperature indicate the coexistence of ferroelectricity and magnetism. The La modification of BiFeO3 has a beneficial effect on the ferroelectric and magnetic properties. The ceramic samples show a stable dielectric constant and quite low dielectric loss between 100 Hz and 10 MHz. The piezoelectric constants of Bi(1−x)LaxFeO3 ceramics were first reported.

Coexistence of ferroelectricity and antiferroelectricity in lead zirconate titanate

The stability balance among the ferroelectric, ferrielectric, and antiferroelectric phases in dielectric materials has been studied by concretely examining the crystallographic features of $\mathrm{Pb}({\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}){\mathrm{O}}_{3}$ samples with $0.07\ensuremath{\leqslant}x\ensuremath{\leqslant}0.20$ by transmission electron microscopy. It was, as a result, found that in this oxide system the increase in the degree of antiferroelectricity into the ferroelectric state resulted in the unique sequence of the phase changes including the appearance of the two-phase state and two ferrielectric phases.

Magnetoelectricity at room temperature in theBi0.9−xTbxLa0.1FeO3system

Magnetoelectric compounds with the general formula, Bi0.9-xRxLa0.1FeO3 (R =Gd, Tb, Dy, etc.), have been synthesized. These show the coexistence of ferroelectricity and magnetism, possess high dielectric constant and exhibit magnetoelectric coupling at room temperature. Such materials may be of great significance in basic as well as applied research.

Electric polarization reversal and memory in a multiferroic material induced by magnetic fields.

Ferroelectric and magnetic materials are a time-honoured subject of study and have led to some of the most important technological advances to date. Magnetism and ferroelectricity are involved with local spins and off-centre structural distortions, respectively. These two seemingly unrelated phenomena can coexist in certain unusual materials, termed multiferroics. Despite the possible coexistence of ferroelectricity and magnetism, a pronounced interplay between these properties has rarely been observed. This has prevented the realization of multiferroic devices offering such functionality. Here, we report a striking interplay between ferroelectricity and magnetism in the multiferroic TbMn2O5, demonstrated by a highly reproducible electric polarization reversal and permanent polarization imprint that are both actuated by an applied magnetic field. Our results point to new device applications such as magnetically recorded ferroelectric memory.

Co-existence of ferroelectricity and ferromagnetism in 1.4 nmSrBi2Ta2O11 film

In pseudo-tetragonal strontium bismuth tantalate,SrBi2Ta2O9 (SBT), with two formula units per unit cell, bismuth oxide{(Bi2O2)2+} layers alternate with double strontium tantalate perovskite layers{(SrTa2O7)2−}.A unit cell of SBT is truncated to form a sub-cell or film, of compositionSrBi2Ta2O11,which is 1.4 nm thick and comprised of a bottom(BiO2)1+ layer, acentral (SrTa2O7)2− layerand a top (BiO2)1+ layer. Using spin-polarized first-principles calculations, it is found that thisSrBi2Ta2O11 film is multi-ferroic, magnetoelectric, i.e. it simultaneously exhibits ferroelectricand ferromagnetic characteristics. When Ta ions are collectively displaced in theab plane and in the [110] direction, the calculated double potential energy well, with a depth of−3.1 eV/unit cell at a Ta off-centre displacement of 0.032 nm, reflects the ferroelectric character. Thecalculated spin-polarized electronic structure reveals that ferromagnetism stems, not fromthe d electrons of the Ta ions, but predominantly from the unpaired p electrons ofthe O ions. The O ions in the Sr–O layer have the largest magnetic moment of1.32 μB. Specifically,the ferromagnetic character is mediated by the unoccupied states of the Sr 5p band above the Fermilevel, EF.These states provide a mechanism for the double exchange or hopping of highly localizedO 2p (majority) spins between adjacent O ions located on both sides of the Sr ion.

Ferroelectric and Ferromagnetic Properties of BiFeO3 Thin Films Deposited by Pulsed Laser Deposition

ABSTRACTBiFeO3 thin film has been prepared on Pt/TiO2/SiO2/Si substrate at a temperature as low as 450°C by pulsed-laser deposition. The BiFeO3 thin film is perovskite single-phase, while any nonperovskite phase, such as orthorhombic Bi2Fe4O9, is not included. Dielectric constant of the film is 87, dielectric loss is 0.03, and leakage current density is low. The coexistence of ferroelectricity and ferromagnetism has been confirmed by means of the P-E and M-H hysteresis characteristics. The BiFeO3 thin film shows a well-saturated hysteresis loop with twice the remanent polarization 2Pr = 54 μC/cm2 and coercive field 2Ec = 100 kV/cm for a maximum applied electric field of 100 kV/cm, and also shows a saturated weak ferromagnetic hysteresis loop, as well as a small remanent magnetization with 2Mr = 0.6 emu/cm3 and 2 Hc = 200 Oe for a maximum magnetic field of 10 kOe at room temperature.

Why Are There so Few Magnetic Ferroelectrics?

Multiferroic magnetoelectrics are materials that are both ferromagnetic and ferroelectric in the same phase. As a result, they have a spontaneous magnetization that can be switched by an applied magnetic field, a spontaneous polarization that can be switched by an applied electric field, and often some coupling between the two. Very few exist in nature or have been synthesized in the laboratory. In this paper, we explore the fundamental physics behind the scarcity of ferromagnetic ferroelectric coexistence. In addition, we examine the properties of some known magnetically ordered ferroelectric materials. We find that, in general, the transition metal d electrons, which are essential for magnetism, reduce the tendency for off-center ferroelectric distortion. Consequently, an additional electronic or structural driving force must be present for ferromagnetism and ferroelectricity to occur simultaneously.

Coexistence of ferroelectricity and ferromagnetism in BiFeO3–BaTiO3 thin films at room temperature

( Bi 0.7 Ba 0.3 ) ( Fe 0.7 Ti 0.3 )O 3 films have been constructed on Nb-doped SrTiO3 (100) by the pulsed-laser deposition technique, and their physical properties have been examined. The films exhibit both ferroelectricity and ferromagnetism (weak ferromagnetism) with Pr=2.5 μC/cm2 and Mr=0.2 emu/g at room temperature. The film-thickness dependence of their magnetic and electric properties (size effect) is also discussed simultaneously. The dielectric constants of the films decrease with reducing film thickness below 1000 Å. The magnetic Curie temperature of the films, on the other hand, does not change at all down to 250 Å.

Coexistence of Ferroelectricity and Antiferromagnetism in Rare Earth Manganese Oxide RMn2O5

Oxides of the group RMn2O5 (R=a rare earth or Y) are simultaneously ferroelectric and antiferromagnetic at low temperatures. The specific features of the phase transitions in this oxide are reviewed with a particular emphasis on the possible interactions between dielectric and magnetic properties.

Competition between hole superconductivity and ferroelectricity in oxides

Abstract The relationship between ferroelectricity and high-temperature superconductivity is investigated. The proposed approach combines an extension of Hirsch's description of the oxygen hole superconductivity and the coupling to an anharmonic lattice. Using standard variational principles, the superconducting order parameter and the static lattice distortion are calculated for certain sets of model parameters. Comparison of the free energies of different possible phases shows to what extent the anharmonic lattice influences superconductivity. This depends mainly on the modulation of the hopping interaction which couples the superconducting subsystem (holes) to the lattice. In particular, the phase boundaries are obtained for different hole concentrations. There is a parameter regime where superconductivity, and ferroelectricity coexist. However, both order parameters (the energy gap and the lattice distortion) are reduced as compared to the pure phases. In the paraelectric regime the anharmonic lattice...

Evidence for coexistence of ferroelectricity and high-T c superconductivity in YBa 2Cu 3O 7-δ (δ < 0.15) from ultrasonic experiments

In order to determine the dielectric properties of the bound charges (soft dipoles) in superconducting YBa 2 Cu 3 O 7-δ (δ < 0.15) we have extended conventional ultrasound experiments to the determination of the dispersion and absorption of the sound-induced rf magnetic field. In contrast to the ultrasonic behaviour, the temperature dependence of the dispersion and absorption of the sound-induced rf magnetic field shows pronounced anomalies. It is shown that these experimental findings are highly indicative for displacive ferroelectric phase transitions appearing in the temperature range of 150 K < T < 180 K and in the vicinity of the superconducting transition temperature. The possible connection between ferroelectricity and high temperature superconductivity is also discussed.