Strong Magnetoelectric Coupling Research Articles

Role of Pb(Zr0.52Ti0.48)O3 on Electric, Dielectric, Electromagnetic Wave Absorption Characteristics of Multiferroic Nanocomposites for Magnetoelectric Devices

Multiferroic composites of ferrite and ferroelcectric phases with systematically varying concentration (100-x)Mg0.48Cu0.12Zn0.4Fe2O4 + x Pb(Zr0.52Ti0.48)O3 (MCZPZT) ( where, x mol% = 0, 20, 40, 50, 60, 80, 100) were prepared by mechanical alloying and sintering methods. The dc resistivity and dielectric constant of the samples as a function of temperature were studied in detail and obtained results are reported. The magnetoelectric effect was investigated for the composites. The sample with 80% ferroelectric phase (MP5), shows largest magnetoelectric output voltage coefficient (dE/dH) H value of 880 μVcm.Oe at 2000 Oe magnetic field. Electromagnetic interference shielding properties of transmission loss and attenuation constant were determined for the composites. Skin depth decreases with frequency from 0.29 to 0.2 cm in the range 8–12 GHz for all composites. The composite MP5 with 80% PZT shows lowest α value between 282 dB m−1 and 414 dB m−1 throughout X-band frequencies. The present results proved that the current magnetoelectric materials of all concentrations exhibit strong magnetoelectric coupling with excellent microwave absorbing performance in X-band region and are appropriate for EMI shielding and novel device applications.

Multiferroic and Phonon Properties of the Double Perovskite Pr2FeAlO6.

With the help of a microscopic model and Green's function technique, we studied the multiferroic and phonon properties of the recently reported new multiferroic Pr2FeAlO6 (PFAO) compound, which belongs to the double perovskite A2BB'O6 family. The magnetization decreases with the increase in temperature and disappears at the ferromagnetic Curie temperature TCFM. The polarization increases with the application of an external magnetic field, indicating strong magnetoelectric coupling and confirming the multiferroic behavior of PFAO. In the curves of dependence of the phonon energy and their damping with respect to temperature, a kink is observed at TCFM. This is due to the strong anharmonic spin-phonon interactions, which play a crucial role below TCFM and are frequently observed in other double perovskite compounds. Above TCFM, only anharmonic phonon-phonon coupling remains. The phonon mode is controlled by an external magnetic field.

Exploration of near room temperature magnetoelectric coupling in BaFe10Sc[formula omitted]O19:KNbO[formula omitted] composite

The consequential experimental endeavour has been undertaken to investigate and control the strain-mediated coupling of the magnetic and electric properties of the composite systems composed of Sc-doped BaFe12O19 and KNbO3. A distinct non-disperse ferroelectric-like anomaly is observed Tkink∼ 265 K, which concomitantly coincides with the magnetic Tcone transition. The observation of external magnetic field dependence dielectric response shows a noticeable decrease in permittivity values, indicating a negative magnetodielectric response. The maximum intrinsic magnetodielectric response is seen in the vicinity of room temperature with the magnetodielectric ratio of 5.4% @ 1 kHz. The linearity of −Δɛ′(H)% vs. M2 plot is phenomenologically described with the Ginzburg–Landau theory with the magnetoelectric coupling term γP2M2. The magnetoelectric coupling relies on strain to induce crystal deformations (flexomagnetoelectric response) on either the ferroelectric phase through magnetostriction or in the magnetic phase through the converse piezoelectric effect. Strain-induced changes in the magnetic as well as dielectric properties of the composites lead to strong magnetoelectric coupling to throw more light exploring a potential candidate for room-temperature multiferroic materials.

Interface enhanced magnetoelectric coupling effect of multiferroic liquids based on CoFe2O4@BaTiO3 core shell particles

A new type CoFe2O4@BaTiO3 (CFO@BTO) multiferroic liquid with different CoFe2O4 (CFO) particle sizes was constructed, and its magnetic properties, electrical properties, and magnetoelectric coupling effects were systematically studied. XRD results show that the CFO phase has a spinel structure, whereas the BaTiO3 (BTO) phase has a perovskite structure, with no obvious heterophase formation. It can be seen from the SEM diagram that the CFO powder has a cuboid shape, and the CFO particle size (1.56 × 0.58 × 0.48 µm, 3.16 × 1.04 × 0.66 µm, 6.47 × 1.53 × 1.40 µm, and 11.19 × 2.64 × 2.28 µm) gradually increased with increasing calcination temperature(T = 450 ℃, 550 ℃, 650 ℃, 750 ℃). TEM results show that the composite particles have obvious core-shell structure. From the hysteresis loop, it can be seen that the saturation magnetization (Ms) of the CFO@BTO powder gradually increases with increasing CFO size. The sedimentation stability of the multiferroic liquid gradually decreases, the dielectric constant and residual polarization (Pr) decrease first and then increase, and the magnetoelectric coefficient and magnetoelectric coupling coefficient increase first and then decrease. When the particle size of the CFO is 6.47 × 1.53 × 1.40 µm, the maximum magnetoelectric coupling coefficient is 210.76 V/(cm·Oe) under an applied magnetic field of 50 Oe, which realizes a strong magnetoelectric coupling effect at room temperature.

A first-principles study on structural stability and magnetoelectric coupling of two-dimensional BaTiO3 ultrathin film with Cr and Cu substituting Ti site

A study on Jahn–Teller distortion reveals that the configuration with Ti-substitution is more stable than that in the case of Ba-replacement. However, magnetoelectric coupling is weak as no spontaneous polarization is formed in the doped unit cell. Taking the atomic radius, low price, and electronegativity into account, Cu was selected to replace Ti together with Cr. Formation energy and phonon spectrum show structural stability. The spontaneous polarization was calculated to be 0.110, 0.114, and 0.247 and 8.078, 0.288, and 0.255 μC/cm2, respectively, in the Cr- and Cu-doped unit cell, corresponding to the directions [100], [010], and [001]. With the application of electric fields, the total magnetic moment was generally enhanced, which resulted in a strong magnetoelectric coupling. In addition, the corresponding coefficient is more than 10 V/cmOe, indicating that the modified BaTiO3 may be a good candidate for single-phase multiferroics. Clearly, co-doping with nonferromagnetic and nonmagnetic elements increases the diversity of new multiferroics.

Fabrication of efficient magnetoelectric multilayered composites via thermal diffusion bonding

Strong magnetoelectric (ME) coupling at low magnetic field under ambient conditions is critical for the development of functional devices. To strengthen the ME coupling specifically in the laminate composite, a new fabrication technique has been proposed namely thermal diffusion bonding. Using this technique, bilayer and trilayer composite of the piezoelectric 72.5Bi0.5Na0.5TiO3–22.5Bi0.5K0.5TiO3–5BiMg0.5Ti0.5O3 (BNKMT) and piezomagnetic Ni0.7Zn0.3Fe2O4 (NZFO) has been synthesized. An enormous ME coefficient for bilayer BNKMT/NZFO (∼ 180.34 mV/cm.Oe) and trilayer BNKMT/NZFO/BNKMT (∼ 287.79 mV/cm.Oe) and NZFO/BNKMT/NZFO (∼ 431.73 mV/cm.Oe) composite has been recorded at extremely low frequency of 10 Hz and biased field of 700 Oe. On comparison with the trilayer composite fabricated via conventional technique (i.e., using conductive epoxy) (∼ 252.12 mV/cm.Oe at 10 Hz and 800 Oe), the direct diffused trilayer composite has displayed relatively 1.7 times higher coupling, which demonstrated its competence. These findings encourage the ME laminate family to add a reliable, relatively easier and cost-effective strategy to its group, which could be beneficial to the improve the performance of modern ME gadgets.

2D/2D coupled MOF/Fe composite metamaterials enable robust ultra–broadband microwave absorption

The combination between macroscopic structure designs and microscopic material designs offers tremendous possibilities for the development of advanced electromagnetic wave (EMW) absorbers. Herein, we propose a metamaterial design to address persistent challenges in this field, including narrow bandwidth, low–frequency bottlenecks, and, particularly, the urgent issue of robustness (i.e., oblique, and polarized incidence). Our absorber features a semiconductive metal-organic framework/iron 2D/2D assembly (CuHT–FCIP) with abundant crystal/crystal heterojunctions and strong magneto-electric coupling networks. This design achieves remarkable EMW absorption across a broad range (2 to 40 GHz) at a thickness of just 9.3 mm. Notably, it maintains stable performance against oblique incidence (within 75°) and polarizations (both transverse electric and transverse magnetic). Furthermore, the absorber demonstrates high specific compressive strength (201.01 MPa·cm3·g−1) and low density (0.89 g·cm−3). This advancement holds promise for developing robust EMW absorbers with superior performance.

Magnetic and dielectric characteristics of rGO modified BFO nanoparticles produced using sol-gel via auto-combustion method

The study examined the structural, optical, dielectric, and magnetic characteristics of Bismuth Ferrite nanoparticles modified by rGO prepared by using the solgel via auto-combustion process. Each sample has a non-uniform surface morphology and a rhombohedral structure with space group R3c. With increasing rGO doping concentrations, the bandgap energy drops, and visible area PL emissions were detected. A frequency dependent dielectric experiment conducted at room temperature (0–1 MHz) reveals that as applied frequencies increase, the dielectric constant and loss factor both drop. The presence of grain and grain boundaries within the particles crystalline structure is shown via impedance analysis. It was discovered that magnetization rise as rGO concentration rise. The BFO and rGO-doped BFO nanoparticles demonstrated strong magnetoelectric coupling.

A dragonfly-wings like self-powered magnetic field sensor with vibration noise restriction function

As the rapid development of the Internet of Things (IoT), the demand for the self-powered sensors and devices has become urgent. In this work, we present a self-powered magnetic field sensor based on a biomimetic dragonfly-wings like magnetoelectric (DWL-ME) laminated cantilever. The two pairs of wings in DWL-ME cantilever operating in anti-phase vibration modal has shown a strong magnetoelectric coupling for converting magnetic field energy into electric energy with an energy harvesting density of as high as 100 µWOe−2cm−3. It also shows a linear response to an alternating magnetic field (HAC) with a high detectability of 2.7 nT at 60 Hz. Compared to traditional cantilever beam ME sensors, its vibration noise is also effectively decreased by more than 30 dB due to the anti-phase vibration modal of two pairs of wings. The proposed biomimetic design strategy has inspirational significance for future sustainable, self-powered intelligent sensor networks.

Exploring the structural, morphological, and multiferroic properties of Al3+ modified (1-x) BCZT-(x) CFO ceramic composites

Multiferroics with strong magnetoelectric coupling can be created by improving the magnetostriction of the ferrite phase and combining it with the best-known piezoelectric. Herein, the ferromagnetic CoFe2O4 was modified with Al incorporation further improve the resistivity, magnetic, and magnetostrictive properties and then combined with (0.5)Ba(Zr0.2Ti0.8)O3−(0.5)(Ba0.7Ca0.3)TiO3 (BCZT) with different weight percentages. XRD results revealed the presence of a mixed spinel cubic phase for CAF (Fd-3m), whereas BCZT crystallized in a tetragonal structure (Amm2) in composite systems. The dielectric response of the materials was studied using impedance spectroscopy and it displayed a typical Maxwell–Wagner polarization of two-phase composites. The magnetic response of the CAF sample improved significantly which is attributed to the preference of Al3+ ions on tetrahedral sites. The magnetization of composites increased as the nonmagnetic BCZT component increased and the (0.75)CAF-(0.25)BCZT system had the highest saturation magnetization. We anticipate that these systems will have significantly improved magnetoelectric characteristics than unmodified CFO-BCZT systems.

Realization of 2D multiferroic with strong magnetoelectric coupling by intercalation: a first-principles high-throughput prediction

The discovery of novel two-dimensional (2D) multiferroic materials is attractive due to their potential for the realization of information storage and logic devices. Although many approaches have been explored to simultaneously introduce ferromagnetic (FM) and ferroelectric (FE) orders into a 2D material, the resulting systems are often plagued by weak magnetoelectric (ME) coupling or limited room-temperature stability. Here, we present a superlattice strategy to construct non-centrosymmetric AM2X4 multiferroic monolayers, i.e., intercalating transition metal ions (A) into the tetragonal-like vacancies of transition metal dichalcogenide bilayers (MX2). Starting from 960 intercalated AM2X4 compounds, our high-throughput calculations have identified 21 multiferroics with robust magnetic order, large FE polarization, low transition barrier, high FE/FM transition temperature, and strong ME coupling. According to the origin of magnetism, we have classified them into twelve type-a, seven type-b, and two type-c multiferroics, which exhibit different ME coupling behavior. During the switching of polarization, the reversal of skyrmions chirality, the transition of the magnetic ground state from FM to antiferromagnetic, and the changes in spin-polarized electron distribution were observed in type-a, type-b, and type-c 2D multiferroic materials, respectively. These results substantially expand the family of 2D ferroic materials and pave an avenue for designing and implementing nonvolatile logic and memory devices.

Two-Dimensional Os2Se3 Nanosheet: A Ferroelectric Metal with Room-Temperature Ferromagnetism.

Two-dimensional (2D) ferroelectric metals (FEMs) possess intriguing characteristics, such as unconventional superconductivity and the nonlinear anomalous Hall effect. However, their occurrence is exceedingly rare due to mutual repulsion between ferroelectricity and metallicity. In addition, further incorporating other features like ferromagnetism into FEMs to enhance their functionalities poses a significantly greater challenge. Here, via first-principles calculations, we demonstrate a case of an FEM that features a coexistence of room-temperature ferromagnetism, ferroelectricity, and metallicity in a thermodynamically stable 2D Os2Se3. It presents a vertical electric polarization of 3.00 pC/m that exceeds those of most FEMs and a moderate polarization switching barrier of 0.22 eV per formula unit. Moreover, 2D Os2Se3 exhibits robust ferromagnetism (Curie temperature TC ≈ 527 K) and a sizable magnetic anisotropy energy (-30.87 meV per formula unit). Furthermore, highly magnetization-dependent electrical conductivity is revealed, indicative of strong magnetoelectric coupling. Berry curvature calculation suggests that the FEM might exhibit nontrivial band topology.

First-principles study on the p-orbital multiferroicity of single-layer XN (X = Ge, Sn, Pb)

Two-dimensional (2D) multiferroic materials have triggered a burst of interest owing to their wide applications in nanoelectronics. Specifically, p-orbital multiferroicity is strongly desired but has been very few reported. Here, based on first-principles calculations, we unveil a new type of 2D multiferroic material: the single-layer (SL) XN (X = Ge, Sn, Pb). Our findings show these materials are ferromagnetic semiconductors with strong magnetoelectric coupling and wide bandgaps. The multiferroicity is related to the unpaired p-orbital electrons of N atoms and the buckled crystal structure. All the single layers show easy-plane magnetocrystalline anisotropy, and the magnetic anisotropy energy increases significantly with the atomic number increasing. Our Monte Carlo simulations suggest the Curie temperature TC is 205.44 K, 200.45 K, and 287.88 K for SL GeN, SnN, and PbN, respectively. By applying tensile strain, the TC can be further increased to 225.39 K, 245.35 K, 369.99 K, respectively. Additionally, biaxial strain can induce semiconductor-to-half-metal and ferroelectricity-to-paraelectricity transition in the single layers. We aspire that our work contributes to the exploration of room-temperature p-orbital multiferroicity.

Single or Vortex Ferroelectric and Ferromagnetic Domain Nanodot Array of Magnetoelectric BiFe0.9Co0.1O3.

Nanodots composed of multiferroic cobalt-substituted BiFeO3, a ferroelectric ferromagnet at room temperature, are fabricated by pulsed laser deposition using anodized porous alumina as masks. The obtained nanodots are approximately 60 nm in diameter, more than 10 nm in thickness, and approximately 70 Gbit/in.2 in density. Piezoresponse and magnetic force microscopies show both ferroelectricity and ferromagnetism with a single-domain nature. It is also found that the dot with 190 nm diameter had multidomain vortex ferroelectric and magnetic structures indicating the strong magnetoelectric coupling. The single-domain cobalt-substituted BiFeO3 nanodots are suitable for verifying magnetization reversal by the electric field, which is the first step in the development of low-power-consumption nonvolatile magnetic memory devices.

First-Principles Study on Evolution of Magnetic Domain in Two-Dimensional BaTiO3 Ultrathin Film Doped with Co under Electric Field.

The magnetization mechanism of Co-doped BaTiO3 ultrathin films is a subject of debate, which results in difficulties with the design of new multiferroics based on BaTiO3 matrixes. With the aid of a first-principles approach, it was observed that when the interstitial site and Ti vacancy were filled with Co, the configuration behaved in a nonmagnetic manner, indicating the significance of the Co content. Moreover, in the case of Co substituting two neighboring Ti atoms, when a direct current field was applied in the [100] direction, the magnetic domains excluding those in the [100], [010], and [001] directions were directed away. Further, the magnetoelectric constant was evaluated at ~449.3 mV/cmOe, showing strong magnetoelectric coupling at room temperature. Clearly, our study indicates that strict control of Ba, Ti, O, and Co stoichiometry can induce an electric and magnetic field conversion in two-dimensional BaTiO3 and may provide a new candidate for single-phase multiferroics for application in next-generation multifunctional devices.

Non-volatile voltage-controlled magnetization in single-phase multiferroic ceramics at room temperature

Single-phase multiferroics (MFs) exhibiting ferroelectricity and ferromagnetism and the strong magnetoelectric (ME) coupling effect at room temperature are seen as key to the development of the next-generation of spintronic devices, multi-state memories, logic devices and sensors. Herein, the single-tetragonal phase (1–x) (Sr0·3Bi0·35Na0·329Li0.021)TiO3-xBiFeO3 (x = 0.2 or 0.4) system was designed to study the intrinsic ME coupling effect at room temperature and high frequencies. The polarization arises from the cooperative displacement of both Fe3+ and Ti4+ relative to the oxygen sublattice in the tetragonally distorted perovskite structure, and the magnetization stems from indirect exchange magnetic interaction between adjacent iron ions. A switchable voltage-controlled magnetization was confirmed by a change of the coercive magnetic field, Hc, and remnant magnetization, Mr, in the x = 0.4 component subjected to an external electric field at room temperature and was possibly attributed to a strain-mediated ME coupling effect. In addition, resonance behaviours of the complex magnetic permeability and complex dielectric permittivity in the GHz band indicate that this ME effect is intrinsic in nature and could broaden the applications of multiferroics to devices operating at microwave frequencies.

Stoner instability-mediated large magnetoelectric effects in 2D stacking electrides

Strong magnetoelectric effects in single-phase two-dimensional (2D) materials are extremely rare in nature. Here by first-principles calculations, we find a strong magnetoelectric coupling in polar stacking bilayer Hf2S that allows the reversal of net magnetic moments with the reversal of electric dipoles. Further analysis shows that such strong magnetoelectric effects benefit from the Stoner instability of surface Hf atoms triggered by polar stacking. Moreover, an unexpectedly large out-of-plane electric polarization (which is at least two times larger than that of bilayer BN) survives in the material, despite its metallicity. The large electric polarization is ascribed to the delocalized interlayer electrons which generally present in layered electride materials. It is quite interesting that large electric polarization, metallicity and magnetism coexist in one single-phase material. Our findings reveal rich physical phenomena to be explored in 2D stacking multiferroics and suggest an alternative way of searching for strong magnetoelectric materials with ultrathin thickness.

Ptychographic Nanoscale Imaging of the Magnetoelectric Coupling in Freestanding BiFeO3.

Understanding the magnetic and ferroelectric ordering of magnetoelectric multiferroic materials at the nanoscale necessitates a versatile imaging method with high spatial resolution. Here, soft X-ray ptychography is employed to simultaneously image the ferroelectric and antiferromagnetic domains in an 80nm thin freestanding film of the room-temperature multiferroic BiFeO3 (BFO). The antiferromagnetic spin cycloid of period 64nm is resolved by reconstructing the corresponding resonant elastic X-ray scattering in real space and visualized together with mosaic-like ferroelectric domains in a linear dichroic contrast image at the Fe L3 edge. The measurements reveal a near perfect coupling between the antiferromagnetic and ferroelectric ordering by which the propagation direction of the spin cycloid is locked orthogonally to the ferroelectric polarization. In addition, the study evinces both a preference for in-plane propagation of the spin cycloid and changes of the ferroelectric polarization by 71°between multiferroic domains in the epitaxial strain-free, freestanding BFO film. The results provide a direct visualization of the strong magnetoelectric coupling in BFO and of its fine multiferroic domain structure, emphasizing the potential of ptychographic imaging for the study of multiferroics and non-collinear magnetic materials with softX-rays.

Spin-Chirality-Driven Multiferroicity in van der Waals Monolayers.

Driven by the expected contribution of two-dimensional multiferroic systems with strong magnetoelectric coupling to the development of multifunctional nanodevices, here we propose, by means of first-principles calculations, vanadium-halide monolayers as a new class of spin-chirality-driven van der Waals multiferroics. The frustrated 120-deg magnetic structure in the triangular lattice induces a ferroelectric polarization perpendicular to the spin-spiral plane, whose sign is switched by a spin-chirality change. It follows that, in the presence of an applied electric field perpendicular to the monolayers, one magnetic chirality can be stabilized over the other, thereby allowing the long-sought electrical control of spin textures. Moreover, we demonstrate the remarkable role of spin-lattice coupling on magnetoelectricity, which adds to the expected contribution of spin-orbit interaction determined by an anion. Indeed, such compounds exhibit sizeable spin-driven structural distortions, thereby promoting the investigation of multifunctional spin-electric-lattice couplings.

Two-Dimensional Asymmetric Multiferroics: Unique Way toward Strong Magnetoelectric Coupling and Multistate Memory.

Two-dimensional (2D) materials have provided a fascinating platform for exploring novel multiferroics and emergent magnetoelectric coupling mechanisms. Here, a novel 2D asymmetric multiferroic based on Janus 2D multiferroic MXene-analogous oxynitrides (InTlNO2) is presented by using first-principles calculations. We find three inequivalent phases for InTlNO2, including two metallic phases (p1 and p2) and one semiconducting phase (p3) with a band gap of 0.88 eV. All phases are room-temperature multiferroics with different Curie temperatures, leading to tunability by phase transitions. We show that there is a 90° rotation of the magnetic anisotropy easy axis between p1 and p2, where p1 favors the in-plane and p2 the out-of-plane easy axis. Therefore, the magnetic anisotropy can be tuned by reversing the out-of-plane polarization. Our strategy provides a unique way toward strong magnetoelectric coupling and multistate memory.