Multiferroic Coupling Research Articles

Tunable sliding ferroelectricity and magnetoelectric coupling in two-dimensional multiferroic MnSe materials

Sliding ferroelectricity (SFE) found in two-dimensional (2D) van der Waals (vdW) materials, such as BN and transition-metal dichalcogenides bilayers, opens an avenue for 2D ferroelectric materials. Multiferroic coupling in 2D SFE materials brings us an alternative concept for spintronic memory devices. In this study, using first-principles calculations, we demonstrate that MnSe multilayers constructed by the recently-synthesized MnSe monolayer have large sliding-driven reversible out-of-plane electric polarization (~10.6 pC m−1) and moderate interlayer sliding barriers superior to the existing 2D SFE materials. Interestingly, the intrinsic electric polarization is accompanied by nonzero net magnetic moments which are also switchable via lateral interlayer sliding. Additionally, both SFE and magnetoelectric coupling can be effectively regulated by external strain and/or hole doping. Our findings suggest the potential of MnSe multilayers in 2D multiferroic and spintronic applications.

Dimerization Triggered Magnetoelectric Coupling Effect and Magnetic Anisotropy in Organic Ternary Crystals.

Developing a new universal strategy to design all organic ferromagnets or multiferroics with satisfactory properties always remains challenging. In this work, ternary charge transfer crystals are fabricated to realize organic multiferroic magnetoelectric coupling effect. Through incorporating the third component into binary crystals, a dimerization between neighbor donor and acceptor is induced to form a lattice symmetry breaking, where a nonpolar to polar phase transition is ensuing to lead to a dipolar polarization. Magnetic field can effectively tune the dipolar polarization to present a magnetoelectric coupling effect. Moreover, the introduction of the third component can result in a rearrangement in molecular configuration to modify the electron-phonon interaction. As a result, anisotropic magnetism is observed due to anisotropic electron-phonon coupling in ternary crystals. Overall, this study forecasts that incorporating an appropriate third component is a potential method for designing all organic multiferroics.

All-electrical reading and writing of spin chirality.

Spintronics promises potential data encoding and computing technologies. Spin chirality plays a very important role in the properties of many topological and noncollinear magnetic materials. Here, we propose the all-electrical detection and manipulation of spin chirality in insulating chiral antiferromagnets. We demonstrate that the spin chirality in insulating epitaxial films of TbMnO3 can be read electrically via the spin Seebeck effect and can be switched by electric fields via the multiferroic coupling of the spin chirality to the ferroelectric polarization. Moreover, multivalued states of the spin chirality can be realized by the combined application of electric and magnetic fields. Our results are a path toward next-generation, low-energy consumption memory and logic devices that rely on spin chirality.

Distinct magnetic contributions for magnetoelectric coupling at room temperature in perovskite PZT-PFN solid solutions

Although a high technological interest, there are only a few single-phase solid solutions that exhibit multiferroic and magnetoelectric coupling at room temperature. In this work, such characteristics are reported for PZT-xPFN solid solutions. It is noticed that magnetoelectric coupling and its nature are anomalously dependent on the PFN concentration, resulting from linear magnetoelectric and paramagnetoelectric contributions. The origin of the multiferroicity and the magnetoelectric coupling is explained by considering the presence and evolution of complex defects and magnetic nanoregions caused by PFN addition. For the lower PFN (x = 0.10), the magnetic order is related to Fe-Vo complex defects. For intermediary Fe-Nb concentration (0.15 <x < 0.25), the equimolar Fe-Nb and well-distributed Fe3+ ions result in a paramagnetic system, without linear magnetoelectric coupling. Finally, for higher Fe-Nb concentrations (0.30 <x < 0.35), the magnetic order is related to the existence of Fe-rich nanoregions, resulting in a linear magnetoelectric coupling three times smaller than that measured for lower PFN content.

Magneto-Electric-Optical Coupling in Multiferroic BiFeO3 -Based Films.

Manipulating ferroic orders and realizing their coupling in multiferroics at room temperature are promising for designing future multifunctional devices. Single external stimulation has been extensively proved to demonstrate the ability of ferroelastic switching in multiferroic oxides, which is crucial to bridge the ferroelectricity and magnetism. However, it is still challenging to directly realize multi-field-driven magnetoelectric coupling in multiferroic oxides as potential multifunctional electrical devices. Here, novel magneto-electric-optical coupling in multiferroic BiFeO3 -based thin films at room temperature mediated by deterministic ferroelastic switching using piezoresponse/magnetic force microscopy and aberration-corrected transmission electron microscopy are shown. Reversible photoinduced ferroelastic switching exhibiting magnetoelectric responses is confirmed in BiFeO3 -based films, which works at flexible strain states. This work directly demonstrates room-temperature magneto-electric-optical coupling in multiferroic films, which provides a framework for designing potential multi-field-driven magnetoelectric devices such as energy conservation memories.

Intrinsic multiferroic MnOF monolayer with room-temperature ferromagnetism

Two-dimensional (2D) multiferroic materials have generated substantial interest owing to the interplay between various ferroic states and the potential applications in miniaturized electronic devices. Using first-principles calculations, we report a ferromagnetic, ferroelectric, and ferroelastic MnOF monolayer, which is an indirect semiconductor with a band gap of 1.8 eV. The Cuire temperature is predicted to be 420 K based on the Monte Carlo simulation of Heisenberg model. The magnetic easy-axis prefers to align along c-axis. Moreover, it shows excellent ferroelectricity with a switchable spontaneous polarization of 7.5 μC/cm2. Meanwhile, MnOF monolayer also habors ferroealsticity with a large reversible strain of 21.4% and a moderate switching energy barrier, which can effectively switchferroelectric polarization direction. MnOF monolayer thus offers a perfect platform for studying the 2D multiferroic coupling effects.

A review on current status and mechanisms of room-temperature magnetoelectric coupling in multiferroics for device applications

A review on current status and mechanisms of room-temperature magnetoelectric coupling in multiferroics for device applications

First observation on emergence of strong room-temperature ferroelectricity and multiferroicity in 2D-Ti3C2T x free-standing MXene film.

Two-dimensional (2D) multiferroics are key candidate materials towards advancement of smart technology. Here, we employed a simple synthesis approach to address the long-awaited dream of developing ferroelectric and multiferroic 2D materials, especially in the new class of materials called MXenes. The etched Ti3C2Tx MXene was first synthesized after HF-treatment followed by a delamination process for successful synthesis of free-standing Ti3C2Tx film. The free-standing film was then exposed to air at room-temperature and heated at different temperatures to form a TiO2 layer derived from the Ti3C2Tx MXene itself. The ferroelectric measurement showed a clear polarization hysteresis loop at room-temperature. Also, due to the reported ferromagnetic behavior of Ti3C2Tx MXene, our composite could show multiferroic properties at room-temperature. The magnetoelectric coupling test was also performed that showed a clear, switchable spontaneous polarization under applied magnetic field. TiO2 is reported to be an incipient ferroelectric that assumes a ferroelectric phase in composite form. The structural and morphological analysis confirmed successful synthesis of free-standing film and the Raman spectroscopy revealed the formation of different phases of TiO2 and the observed ferroelectricity could be due to structural deformation as a result of the formation of this new phase. The measured value of remanent polarization is 0.5 μC cm−2. This is the first report on the existence of a ferroelectric phase and multiferroic coupling in 2D free-standing MXene film at room-temperature which opens-up the possibility of 2D material-based electric and magnetic data storage applications at room-temperature.

Multiferroic Coupling of Ferromagnetic and Ferroelectric Particles through Elastic Polymers.

Multiferroics are materials that electrically polarize when subjected to a magnetic field and magnetize under the action of an electric field. In composites, the multiferroic effect is achieved by mixing of ferromagnetic (FM) and ferroelectric (FE) particles. The FM particles are prone to magnetostriction (field-induced deformation), whereas the FE particles display piezoelectricity (electrically polarize under mechanical stress). In solid composites, where the FM and FE grains are in tight contact, the combination of these effects directly leads to multiferroic behavior. In the present work, we considered the FM/FE composites with soft polymer bases, where the particles of alternative kinds are remote from one another. In these systems, the multiferroic coupling is different and more complicated in comparison with the solid ones as it is essentially mediated by an electromagnetically neutral matrix. When either of the fields, magnetic or electric, acts on the ‘akin’ particles (FM or FE) it causes their displacement and by that perturbs the particle elastic environments. The induced mechanical stresses spread over the matrix and inevitably affect the particles of an alternative kind. Therefore, magnetization causes an electric response (due to the piezoeffect in FE) whereas electric polarization might entail a magnetic response (due to the magnetostriction effect in FM). A numerical model accounting for the multiferroic behavior of a polymer composite of the above-described type is proposed and confirmed experimentally on a polymer-based dispersion of iron and lead zirconate micron-size particles.

Suppression of ferroelectric polarization and hence room temperature multiferroicity of LuFeO3 on Cu and Mn doping

Room temperature multiferroicity has been in the centre of interest for last few years due to its enormous potential to be applied as real multifunctional device. LuFeO3 is a potential candidate as room temperature multiferroic1, which offers strong multiferroic coupling at room temperature [1]. Presence of ferroelectric polarization is observed in Mn-doped LuFeO3 also. The main area of restriction is its low polarization, which is to be improved before it can be applied in real devices. In order to do that proper understanding of the mechanism of generation of ferroelectricity is needed. In order to do that we observed that, the ferroelectric and multiferroic properties at room temperature, in orthorhombic distorted perovskite LuFeO3 are greatly affected by Cu or Mn doping. If we replace Fe+3 ion (Ionic Radius=126) with some amount another ion of increasing ionic radius Mn+2 (Ionic Radius=127) and Cu+2 (Ionic Radius = 128) the ferroelectric properties are greatly affected as evidenced by the P-E Hysteresis loop measurements. The appearance of ferroelectricity in LuFeO3 could be attributed to the spin current based model as proposed by katsura et al. [3]. The effect of Cu and Mn doping also can be explained with the Spin current based model [3]. Copyright © 2017 VBRI Press.

Sliding ferroelectricity in 2D van der Waals materials: Related physics and future opportunities

Near the 100th anniversary of the discovery of ferroelectricity, so-called sliding ferroelectricity has been proposed and confirmed recently in a series of experiments that have stimulated remarkable interest. Such ferroelectricity exists widely and exists only in two-dimensional (2D) van der Waals stacked layers, where the vertical electric polarization is switched by in-plane interlayer sliding. Reciprocally, interlayer sliding and the “ripplocation” domain wall can be driven by an external vertical electric field. The unique combination of intralayer stiffness and interlayer slipperiness of 2D van der Waals layers greatly facilitates such switching while still maintaining environmental and mechanical robustness at ambient conditions. In this perspective, we discuss the progress and future opportunities in this behavior. The origin of such ferroelectricity as well as a general rule for judging its existence are summarized, where the vertical stacking sequence is crucial for its formation. This discovery broadens 2D ferroelectrics from very few material candidates to most of the known 2D materials. Their low switching barriers enable high-speed data writing with low energy cost. Related physics like Moiré ferroelectricity, the ferroelectric nonlinear anomalous Hall effect, and multiferroic coupling are discussed. For 2D valleytronics, nontrivial band topology and superconductivity, their possible couplings with sliding ferroelectricity via certain stacking or Moiré ferroelectricity also deserve interest. We provide critical reviews on the current challenges in this emerging area.

Monolayer puckered pentagonal VTe2: An emergent two-dimensional ferromagnetic semiconductor with multiferroic coupling

Monolayer puckered pentagonal VTe2: An emergent two-dimensional ferromagnetic semiconductor with multiferroic coupling

Multiferroic magnetoelectric coupling effect of three-layer multiferroic (Ba0.6Sr0.4TiO3–Ni0.6Zn0.4Fe2O4)3 heterojunction fabricated by sol–gel process

Multiferroic magnetoelectric coupling effect of three-layer multiferroic (Ba0.6Sr0.4TiO3–Ni0.6Zn0.4Fe2O4)3 heterojunction fabricated by sol–gel process

Hydrothermal synthesis of Bi2Fe4O9 nanochains and study of their multiferroic coupling

We report synthesis of self-assembled Bi2Fe4O9 nanochains by hydrothermal method using Oleic acid as a surfactant which plays an important role in the self-assembled nanochain formation. Temperature dependent dc magnetization study suggests downward shift of the Neel temperature TN ~ 63 K for the particles of size ~ 22 nm while it is reported to be ~ 260 K in the bulk sample. The magnetic hysteresis (M−H) loops offer evidence of weak ferromagnetism across the entire temperature range 10–300 K. Exchange coupling across the interface between coexisting ferromagnetic and antiferromagnetic orders gives rise to a small amount of exchange bias at low temperature. The sample also exhibits substantial magnetoelectric multiferroic coupling at room temperature with ~77% suppression of ferroelectric polarization under 10 kOe magnetic field.

Magnetodielectric Response in a Layered Mixed-Valence Ferrimagnetic Molecular Compound.

The magnetodielectric effect is closely related to multiferroic or magnetoelectric coupling; thus, it can be used to predict magnetoelectric coupling, especially in compounds with special magnetic properties. The magnetodielectric response can often be used to predict many interesting and meaningful physical coupling mechanisms. Therefore, fabricating magnetodielectric materials is an effective step toward the development of magnetoelectric materials. Herein, we synthesize the mixed-valence layered ferrimagnetic molecular compound (C6N2H14)FeIII2FeIIF8(HCOO)2 (1) and demonstrate that it exhibits both slow magnetic relaxation behavior and long-range magnetic order. This long-range order occurs because of the coexistence and competition between two typical magnetic interactions, namely, an FeIII-F-FeII superexchange and a long-distance superexchange FeII-O-C-O-FeIII-F-FeIII path in the interlayer and interchain spin frustration. Notably, this compound also demonstrates two abnormal dielectric relaxation processes: the first process is dominated by dynamic guest cations, while the other process is related to the increasing magnetic correlation. Over a wide temperature range below 170 K, the magnetodielectric effect reveals that the magnetic correlation maybe promotes electron dynamics and leads to magnetodielectric coupling. These findings pave a novel path for designing magnetodielectric molecular materials.

Magnetoelectric Coupling Triggered by Noncollinear Magnetic Structure in M‐Type Hexaferrite

AbstractDirect magnetoelectric (ME) coupling between magnetic and ferroelectric orders, which can be realized in spiral magnets, is vital in technological applications of multifunctional materials. Multisusceptible BaFe12O19 is noteworthy for its excellent magnetic, dielectric properties and thus the application in high‐density information storage, while its collinear spin structure limits the emergence of ferroelectrics and ME coupling. In this work, nonzero Dzyaloshinskii–Moriya (DM) interaction is created by partial substitution of the spin‐down Fe3+ sites to induce conical spin structure in BaFe12O19. Larger In3+ ions are introduced and prefer to occupy the spin‐down 4f1 and 4f2 lattice sites. The evolution of magnetization versus temperature adduces evidence of conical magnetic structure. As a result, direct ME and magnetodielectric coupling are obtained in In‐doped BaFe12O19 ceramics. An interlayer DM interaction model is built to discuss the intrinsic relationship among crystal structure, noncollinear magnetic structure, and ionic substitution. Moreover, BaZn0.9Zr0.9Fe10.2O19 ceramics are also prepared, and exhibit noncollinear magnetic structure and direct ME coupling since Zn2+ and Zr4+ also possess larger radii than Fe3+ and prefer to enter the spin‐down sites. The present result provides a feasible avenue to develop multiferroic and magnetoelectric coupling in ubiquitous M‐type hexaferrite.

MgFe2O4/(Ba0·85Ca0.15) (Zr0·1Ti0.9)O3 lead free ceramic composite: A study on multiferroic and magnetoelectric coupling properties at room temperature

MgFe2O4 (MFO) and (Ba0·85Ca0.15) (Zr0·1Ti0.9)O3 (BCZT) was prepared by solid state route and are found to be ferromagnetic and ferroelectric at room temperature respectively. MFO/BCZT composite (50:50 M concentration of MFO and BCZT) was also prepared by solid state route. Multiferroic properties of MFO/BCZT ceramic composite were investigated. Scanning electron micrograph confirms the distribution of small grains of MFO around large grain of BCZT for proper surface interaction. MFO/BCZT composite exhibits saturated magnetization of 12 emu/gm, which reduce to 10 emu/gm on electrical poling at 2.5 kV/cm indicating magneto-electric coupling between MFO and BCZT through interface interaction. The composite also exhibits proper ferroelectric polarization, which is confirmed from I–V characteristic plot (occurrence of double minima as that of proper ferroelectric). The transverse magnetoelectric coupling coefficient (αV31) for this composite is found to be 7.97 mVcm−1Oe−1 at 10 kHz. MFO/BCZT ceramic composite exhibit multiferroic and magnetoelectric coupling properties for 50:50 M concentration at room temperature may be suitable for device applications.

Coupling of Lamb Waves and Spin Waves in Multiferroic Heterostructures

In this work, we investigate magneto-acoustic attenuation in thin film multiferroic Lamb wave delay lines. By leveraging magneto-acoustic interactions, multiferroics have potential to realize passive chip-scale alternatives to bulky ferrite devices. For the first time, magnetic field dependence of magneto-acoustic interactions in multiferroic Lamb wave devices is characterized. Multiferroic heterostructures of aluminum nitride and cobalt iron boron are fabricated into Lamb wave delay lines operating at 7.492 GHz to study the effect of strain nonuniformity on the multiferroic coupling. The attenuation of the Lamb waves is characterized as a function of the magnitude and angle of an applied in-plane bias magnetic field. It is found that the bias magnitude for peak attenuation is a strong function of angle, indicating that it is due to coupling between the Lamb waves and spin wave modes. This is in contrast with current models of attenuation in multiferroic SAW delay lines, where the uniform surface strains couple to ferromagnetic resonance, which has no angular dependence on the in-plane bias field magnitude. These results are the first steps towards passive chip-scale alternatives to ferrite devices utilizing Lamb wave devices, which have better coupling and scalability than their SAW counterparts. [2020-0114]

Impact of transition metal oxidation state on the multiferroic properties and magnetoelectric coupling strength of BST ceramics

ABSTRACT Effect of starting Fe precursor (Fe2O3 and Fe3O4) on the multiferroic properties of BST (Ba0.96Sr0.04Ti0.91Fe0.09O3) ceramics has been investigated. Considerable changes in the ferroelectric and magnetic properties of these ceramics were observed. High crystallinity, tetragonal structure and phase purity of both the samples were confirmed using X-ray diffraction analysis. The field emission scanning electron microscopy analysis confirmed the uniform grain growth in both the samples with an average grain size of ≈0.40 μm. X-ray photoelectron spectroscopy analysis confirmed the presence of Fe2+ only and both Fe2+ and Fe3+ in Fe2O3- and Fe3O4-doped samples. The Fe3O4-doped BST samples displayed higher Pr and Mr values (2.32 μC/cm2and 0.012 emu/g) as compared to Fe2O3-doped BST samples. The M-E coupling response (≈10.56%) too was observed to be more pronounced in Fe3O4-doped BST samples. Our research work suggests that Fe3O4 doping in BST is better suited for multiferroic applications due to the presence of multivalent Fe ions.

Magnetic properties of aligned multiferroic Janus nanofiber agglomerates measured with the scattered magneto-optical Kerr effect

We report magnetic properties of electrospun multiferroic nanofibers assembled into linear aggregates with an external magnetic field, and measured with the magneto-optical Kerr effect (MOKE) in a non-specular or scattering geometry (ScMOKE). Compared with bulk magnetometry, ScMOKE’s sensitivity to subtle differences between aggregates offers a route to determine local multiferroic coupling in disordered nanomaterials. CoFe2O4-BaTiO3 nanofiber agglomerates are assembled prior to measurement by suspending and aligning the fibers in a transparent air-cured polyvinyl alcohol solution. We detect the polarization change in light scattered from the fibers, collected at an off-specular angle in order to eliminate the background caused by substrate reflection. Averaged hysteresis loops from different agglomerates show a variety of unique structures. For our optical spot size of ∼15 m, multiple fibers, within a single agglomerate, are detected simultaneously, suggesting ScMOKE can distinguish local magnetization reversal fields that vary from fiber to fiber, as well as magnetic interactions between fibers.