Magnetoelectric Coupling Research Articles

Multiferroicity and Semi‐Cylindrical Alignment in Janus Nanofiber Aggregates

Abstract1D multiferroic fibers are known to exhibit attractive characteristics, including enhanced magnetoelectric (ME) coupling compared to thin film and bulk architectures. A comprehensive understanding of composite fibers, however, has been hindered by the complexity of their structure, leading to limited reports. Here, clear and strong ME coupling is experimentally detected in a composite Janus nanofiber aggregate using second harmonic generation (SHG) polarimetry under different magnetic field orientations. The observation of such a pronounced effect using an all‐optical method has not been previously reported in multiferroic fibers. A series of global fits is performed to the SHG polarimetry results to investigate the behavior of nanofibers within an aggregate. We find the magnetically assembled fibers exhibit semi‐cylindrical alignment as well as the expected lengthwise alignment despite variations in size and composition from fiber to fiber. The ME coupling and the semi‐cylindrical alignment seen in SHG are further corroborated via X‐ray diffraction under similar magnetic field conditions. These findings contribute to the development of complex composite and multifunctional devices using multiferroic nanostructures as building blocks, even those with inhomogeneous shapes and geometries.

Magnetoelectric Coupling in a Mn4Na-Organic Complex under Pulsed Magnetic Fields up to 73 T.

Research on the magnetoelectric (ME) effect (or spin-electric coupling) in molecule-based magnetic materials is a relatively nascent but promising topic. Molecule-based magnetic materials have diverse magnetic functionalities that can be coupled to electrical properties. Here we investigate a realization of ME coupling that is fundamental but not heavily studied─the coupling of magnetic spin level crossings to changes in electric polarization. A mixed-valence Mn4Na complex with a total ground-state spin S = 5/2 under zero magnetic field and S = 17/2 under high magnetic field undergoes a cascade of ground-state level crossings of the Sz states with increasing magnetic field. Magnetization and electrical polarization measurements under pulsed magnetic fields up to 73 T show that each spin level crossing is accompanied by a significant change in electric polarization that is an even function of the applied magnetic field. A molecular Hamiltonian describing antiferromagnetic exchange in a distorted tetrahedron of three MnIII and one MnII ions matches the data well. We conclude that the ME coupling is caused by magnetostriction within the polar molecule as it distorts to lower its magnetic exchange energy.

Flexible magnetoelectric systems: Types, principles, materials, preparation and application

Recently, the rapid development of flexible electronic materials and devices has profoundly influenced various aspects of social development. Flexible magnetoelectric systems (FMESs), leveraging magnetoelectric coupling, hold vast potential applications in the fields of flexible sensing, memory storage, biomedicine, energy harvesting, and soft robotics. Consequently, they have emerged as a significant branch within the realm of flexible electronic devices. According to its working principle, FMES are divided into three categories: FMES based on magnetodeformation and piezoelectric effects, FMES based on giant magnetoresistive effect, and FMES based on electromagnetic induction. Although some articles have reviewed the first two types of FMES, there is a lack of systematic introduction of the FMES based on electromagnetic induction in existing studies, especially the development history and research status of the three types of FMES. Therefore, this paper systematically reviews the development history and research status of these three kinds of FMES and reveals the working principle and mode of the flexible magnetoelectric system from the perspective of the force-electricity-magnetism coupling mode. In addition, the material selection criteria, device manufacturing methods, and application fields of the FMES are also introduced. Finally, this review delves into the challenges and opportunities confronting the development of FMES, exploring the future development directions. This review aims to establish a theoretical foundation and provide methodological strategies for future research on FMES. It is anticipated to promptly address the current gap in this research field and facilitate the development of the flexible electronic family.

Dual magnetoelectric antenna array with enhanced bandwidth and sensitivity for low-frequency communications

The magnetoelectric coupling effect demonstrated immense potential for miniaturizing antenna applications. However, due to the resonant nature of magnetoelectric (ME) antennas, their bandwidth tended to be relatively narrow. To address this limitation, our study introduced an array design based on coupled ME antennas. A tri-layer FeGa–PZT8–FeGa laminate structure was employed to construct the ME antennas, which utilized inter-array coupling to broaden the frequency range. Both the central frequency and sensitivity of the array structure were theoretically analyzed, and two methods for extending the frequency were proposed. By coupling two ME antennas of similar frequency in the series mode, the arrayed ME antennas exhibited enhanced sensitivity, increasing from 0.225 and 0.247 to 0.413 mV/nT, and an expanded bandwidth from 0.92–1.03 to 1.4 kHz, indicating improved performance through combined configuration. On the other hand, by coupling two ME antennas of different frequencies together in the series mode, a dual-frequency (97.8/98.97 kHz) ME antenna array was formed. The communication capabilities of the ME antenna array under weak magnetic fields were demonstrated using amplitude shift keying and frequency shift keying modulation methods. The designed array of ME antennas elevated low-frequency communication performance and possessed excellent magnetic field detection capabilities, thereby offering a cost-effective technological pathway for bioelectronic and marine communication design.

Localized Flexoelectric Effect Around Ba(CuNb) Nano‐Clusters in Epitaxial BiFeO3 Films for Enhancement of Electric and Multiferroic Properties

AbstractRoom‐temperature (RT) multiferroic materials have received significant research attention for various potential applications; however, their properties are not suitable for real‐world implementation. In this study, a nano‐scale localized flexoelectric effect is introduced to enhance the RT multiferroic performance of epitaxial bismuth iron oxide (BiFeO3; BFO) thin films by embedding 10 mol% Ba(Cu1/3Nb2/3)O3 (BCN) nano‐clusters into the host BFO film, which originally has a rhombohedral crystal structure. By utilizing nano‐clustering, a large out‐of‐plane coherent strain is localized around the nano‐clusters, resulting in a highly strained tetragonality of the BFO structure; subsequently, the films exhibit peculiar types of domains and domain walls, such as nano‐scale rotational vortices and antiparallel dipole configurations. These peculiar domain structures, which originate from the localized flexoelectric effect at the nano‐scale, enable excellent ferroelectric, ferromagnetic, and RT multiferroic magnetoelectric coupling. This study reveals that the local variation in the localized flexoelectric field around nano‐clusters considerably impacts the formation of unusual domain‐wall structures. This suggests that the controlled introduction of nano‐clusters with different crystal structures is promising for achieving the desired multiferroic properties.

Study on the Microstructure and Performance of the Multi-Field Composite-Assisted Laser Cladding of Nickel-Based Tungsten Carbide Coatings

Improving the hardness and wear resistance of die cutting tools is an important issue in the study of the service life of die cutting equipment. Using laser cladding technology, nickel-based composite coatings with varying BiFeO3 contents were prepared on a 45 steel substrate, because BiFeO3 can have an effect on the dilution rate and microstructure of the sample; morover BiFeO3 is a new type of multiferroic material with certain magneto-electric coupling effects which can be prepared for the study of added magnetic fields. The microstructure and morphology were characterized to determine the optimal BiFeO3 content. Based on the optimal addition of BiFeO3, a comparative analysis was conducted to investigate the effect of different magnetic field strengths under a composite energy field on the microstructure, hardness, and wear resistance of Ni-based WC cladding layers. The results show that the optimal addition of BiFeO3 was 5 wt%. At this concentration, there were no significant porosity defects in the coating, and the dilution rate was appropriate (4.77%). Additionally, the interface bonding strength was also increased. With optimal BiFeO3 addition, stirring with different magnetic field strengths was applied to the cladding layer, and the results show that the aspect ratio of the cladding layer gradually increased with increasing the alternating magnetic field strength. When the magnetic field strength in the composite energy field was 40 mT, the microstructure was fine and uniform, the hardness of the cladding layer reached the highest level, about 925.2 HV1.0, the wear resistance was also the best, the friction coefficient of the cladding layer was about 0.54, and the width of the wear mark was about 0.53 mm.

Direct magnetoelectric coupling in Pr doping Bi6Ti3Fe2O18 relaxor ferroics

Single-phase multiferroics are fractional and rarely meet at room temperature. Direct magnetoelectric coupling in relaxor ferroic phase was observed in Bi6−xPrxTi3Fe2O18 (x = 0.0, 0.3, 0.6, 0.9, and 1.2) films, where the chemical disorder doping-induced effective internal pressure played a key role. It is analytically formulated from the phase-structure shift, ferroelectric domain, and origin of the magnetic order. The strip magnetic domains are broken into a dotted domain structure following a quantitatively increase in lattice stress. A Monte Carlo simulation including stress energy items is used to unveil the hitherto unexplored coupling mechanism by tuning the symmetric exchange restriction of Fe3+–O–Fe3+. Moreover, the observation of coefficient 78.8 mV/cm·Oe at room temperature is intriguing for potential application.

Magnetoelectric nanodiscs enable wireless transgene-free neuromodulation.

Deep brain stimulation with implanted electrodes has transformed neuroscience studies and treatment of neurological and psychiatric conditions. Discovering less invasive alternatives to deep brain stimulation could expand its clinical and research applications. Nanomaterial-mediated transduction of magnetic fields into electric potentials has been explored as a means for remote neuromodulation. Here we synthesize magnetoelectric nanodiscs (MENDs) with a core-double-shell Fe3O4-CoFe2O4-BaTiO3 architecture (250 nm diameter and 50 nm thickness) with efficient magnetoelectric coupling. We find robust responses to magnetic field stimulation in neurons decorated with MENDs at a density of 1 µg mm-2 despite individual-particle potentials below the neuronal excitation threshold. We propose a model for repetitive subthreshold depolarization that, combined with cable theory, supports our observations in vitro and informs magnetoelectric stimulation in vivo. Injected into the ventral tegmental area or the subthalamic nucleus of genetically intact mice at concentrations of 1 mg ml-1, MENDs enable remote control of reward or motor behaviours, respectively. These findings set the stage for mechanistic optimization of magnetoelectric neuromodulation towards applications in neuroscience research.

Magnetoelectric Tuning of 2D Ferromagnetism in 1T-CrTe2 through In2Se3 Substrate.

Electric field control of two-dimensional (2D) materials with optimized magnetic properties is not only of scientific interest but also of technological importance in terms of the functionality of various nanoscale devices. Here, we report the multiferroic control of the 2D ferromagnetism in 1T-CrTe2 monolayer through a ferroelectric In2Se3 sublayer. Our results reveal the effect of polarization switching on the electronic structures and magnetic properties of 1T-CrTe2/In2Se3 heterostructures, enabling effective manipulation of their magnetic anisotropy energy (MAE) and magnetization orientation. Additionally, we also demonstrate the strong dependence of their MAE and switching effect on the external strain and surface hydrogenation. Notably, polarization switching exhibits a reversal modification in the hydrogenated multiferroic structures. These tunable behaviors are primarily attributed to the alteration of p-orbitals near the Fermi level of the interfacial Te atoms due to magnetoelectric coupling. Our findings suggest the potential of 1T-CrTe2/In2Se3 heterojunctions for the practical application of 2D multiferroic spintronic devices.

Tunable Schottky barriers and magnetoelectric coupling driven by ferroelectric polarization reversal of MnI3/In2Se3 multiferroic heterostructures

Two-dimensional (2D) multiferroic materials are recognized as promising candidates for next-generation nanodevices due to their tunable magnetoelectric coupling and distinctive physical phenomena. In this study, we proposed a novel 2D multiferroic van der Waals heterostructure (vdWH) by stacking atomic layers of ferroelectric In2Se3 and ferromagnetic MnI3. Using first-principles calculations, we found that the MnI3/In2Se3 vdWH exhibit robust metallic conductivity across various spin and polarization states, preserving the distinctive band characteristics of isolated In2Se3 and MnI3. However, the alignment of Fermi levels causes the conduction band minimum (CBM) and valence band maximum (VBM) of In2Se3 and MnI3 to shift relative to their original band structures. Remarkably, the MnI3/In2Se3 with the upward polarization state of In2Se3 exhibits an Ohmic contact. Switching the polarization direction of In2Se3 from upward to downward can transform the MnI3/In2Se3 vdWH from an Ohmic contact to a p-type Schottky contact, while also modifying its dipole moment, magnetic strength and direction. Based on these properties of MnI3/In2Se3 vdWH, we designed the field-effect transistors (FETs) with high on/off rates and nonvolatile data storage device. Furthermore, the Schottky barrier heights (SBHs), magnetic moment, and dipole moment of MnI3/In2Se3 vdWH can also be effectively regulated by reducing the interlayer distance. With the continuous reduction of the interlayer distance of MnI3/In2Se3 vdWH, its easy magnetization axis is expected to shift from in-plane to out-of-plane. These findings offer new insights for the design and development of the next-generation spintronic and nonvolatile memory nanodevices.

Coexistence of ferroelectricity and antiferroelectricity in 2D van der Waals multiferroic

Multiferroic materials have been intensively pursued to achieve the mutual control of electric and magnetic properties. The breakthrough progress in 2D magnets and ferroelectrics encourages the exploration of low-dimensional multiferroics, which holds the promise of understanding inscrutable magnetoelectric coupling and inventing advanced spintronic devices. However, confirming ferroelectricity with optical techniques is challenging in 2D materials, particularly in conjunction with antiferromagnetic orders in single- and few-layer multiferroics. Here, we report the discovery of 2D vdW multiferroic with out-of-plane ferroelectric polarization in trilayer NiI2 device, as revealed by scanning reflective magnetic circular dichroism microscopy and ferroelectric hysteresis loops. The evolution between ferroelectric and antiferroelectric phases has been unambiguously observed. Moreover, the magnetoelectric interaction is directly probed by magnetic control of the multiferroic domain switching. This work opens up opportunities for exploring multiferroic orders and multiferroic physics at the limit of single or few atomic layers, and for creating advanced magnetoelectronic devices.

Fabrication of hexagonal platelets of Fe3O4/Fe2O3/C modified with polyacrylamide for excellent electromagnetic wave absorption

In order to improve the weak dielectric loss capability and poor impedance matching of Fe3O4, the hexagonal plates of Fe3O4/Fe2O3/C nanocomposites were rationally constructed in this paper by utilizing electrostatic attraction and cross-linking, using polyacrylamide (PAM) as templating agent and viscosity modifier. The stacked hexagonal plates constructed a conductive network and utilized the structural properties of Fe3O4 to promote the transfer and jump of free electrons, which effectively improved the conduction loss. The heterogeneous interface was effectively constructed due to the presence of Fe2O3 and trace carbon, while the transfer and leap of free electrons promoted the generation of interfacial polarization, resulting in magnetoelectric coupling and effective improvement of polarization loss. The results show that the effective absorption broadband reaches 4.08 GHz when the matching thickness of the composite is 2 mm. A minimum reflection loss of −43.79 dB is realized at a matching thickness of 1 mm. The PAM modification proved to be an effective means to modulate the morphology and composition of the materials.

Oxygen vacancy induced electrical conductivity enhancement in Ca-doped BiFeO3 thin films

Bismuth ferrite, recognized for its exceptional physical properties as a multiferroic material, has recently attracted considerable attention due to its high domain wall conduction. However, challenges in further improving domain wall conductivity and magnetoelectric coupling hamper the practical application of pure-phase BFO thin films. Addressing these limitations, we successfully synthesized Bi1-xCaxFeO3 thin films on LaAlO₃ (001) substrates with varied calcium (Ca) doping levels (x = 0–0.3) through pulsed laser deposition. Our experimental data demonstrate a direct relationship between the films' electrical conductivity and the prevalence of oxygen vacancies (OV). An upward trend in both OV density and electrical conductivity emerges with incremental Ca doping, peaking at x = 0.2. Beyond this doping threshold, a further increase in Ca concentration inversely affects OV density and electrical conductivity. These insights suggest that fine-tuning OV concentration in Ca-doped BFO thin films can significantly modulate their electrical properties, paving the way for the advancement of bismuth ferrite-based electronic devices.

Structural evolution and enhanced multiferroicity in BiFeO3-based ceramics via rare earth element co-substitution

In this study, multiple rare earth elements were introduced to modify the multiferroic properties of BiFeO3. The effects of co-substitution on the structural evolution and properties were thoroughly investigated. With increasing substitution content, the ceramics underwent a symmetry transition from R3c to Pna21 and finally to Pbnm. Co-substitution significantly enhanced the ferroelectric properties, with the highest remanent polarization of 33.14 μC/cm² observed at x = 0.10. Due to the symmetry evolution, ferromagnetism was released from the cycloidal spin structure, and the hysteresis loop gradually saturated, with the highest remanent magnetization (Mr) of 0.25emu/g observed at x = 0.16. The concurrent improvement in ferroelectricity and ferromagnetism resulted in substantial magnetoelectric coupling performance, with αME = 3.50mV/(cm·Oe). Moreover, direct current poling significantly induced the reverse transition from R3c to Pna21, indicating the potential for electrically controlled magnetism. This study provides a new perspective for modifying the magnetoelectric properties of BiFeO3.

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.

Bias voltage modulated electric transport properties in Fe65Co35/Hf0.5Zr0.5O2 films

We demonstrate the bias voltage modulated electric transport properties in Fe65Co35 (FeCo) films deposited on Hf0.5Zr0.5O2 (HZO) films. Intrinsic multiferroicity have been characterized for the FeCo/HZO heterostructures by analyzing the ferroelectric polarizations and imaging the magnetic domains. We show that, upon the application of bias voltages on the FeCo/HZO heterostructures, the current-voltage (I-V) curves of FeCo films can be regulated, giving rise to different resistance states, enabled partly by strain-mediated magnetoelectric coupling effect. The strain coupling effect between HZO and FeCo films is elucidated by simulating the volumetric strain of the FeCo/HZO films under the action of applied voltages. Through additional analysis, the bias voltage modulated electric transport properties could also be linked with charge-mediated magnetoelectric coupling effect. We anticipate that our work will inspire further studies on low-power consumption and high-density electronic devices.

Hybrid multilayer magnetoelectric coupling based on magnetostrictive materials

Multiferroic materials have a unique ability to combine two or more ferroic orders within the same phase. Specifically, magnetoelectric (ME) materials exhibit a unique combination of three ferroic orders in their response to magnetic, elastic, and electric fields. This study focuses on a finite element investigation of a hybrid multilayer ME coupling, incorporating two different magnetostrictive materials in a single composite. The composite includes Nickel, exhibiting negative magnetostriction, leading to an increase in pre-compressive stress, easy machinability, and cost-effectiveness. Additionally, Terfenol-D is utilized due to its characteristic property of high magnetostrictive strain when exposed to an external magnetic field. The result of this study shows that this hybrid ME structure has an ME coefficient of 804 mV/cm ⋅ Oe without pre-stress and ME coefficient is increased to 32.64 V/cm ⋅ Oe by applying pre-stress while retaining cost-effectiveness. The analysis in this particular work also suggests promising applications for energy harvesting and magnetic field sensing.

Piezostrain control of orbital Rashba effect in Py/CuOx/PMN-PT heterostructures

Electric-field modulated magnetic properties have attracted numerous research studies to elucidate the underlying physics and develop practical electronic devices. In this work, it is demonstrated that the orbital Rashba effect can be modulated by the applied electric field, which is reflected by the variation of charge-to-orbital conversion efficiency ξ under different electric fields in Py/CuOx/PMN-PT heterostructures, where ξ displays a butterfly-like behavior with the electric field, which can be attributed to the piezostrain-mediated magnetoelectric coupling, thus realizing the effective modulation of orbital torque related to the orbital Rashba effect. In addition, our first-principles calculations demonstrate that the orbital moment increases upon increasing strain, which stems from the enhanced p–d hybridization of the interfaced O and Cu atoms. Our results provide a method for modulating the orbital Rashba effect and charge-to-orbital conversion, which shows good potential for practical applications.

Multi-heterogeneous interfaces boost dielectric polarization in PBA-derived Co/MnO@NC ternary composites for electromagnetic wave absorption

The elaborate construction of multi-component composites has been deemed as a promising strategy to enhance dielectric polarization response capability in the preparation of highly efficient microwave absorbers. However, the rational design and integration of homogeneous composites with diverse components continues to pose a great challenge. Herein, we propose a straightforward self-assembly-carbonization strategy for fabricating Co/MnO@NC ternary composites derived from CoMn-Prussian Blue Analogous precursors, featuring enriched heterogeneous interfaces and balanced magneto-electric coupling synergy. The ternary composites effectively introduce diverse dissipation mechanisms, including interfacial polarization behavior originated from the constructed heterogeneous interfaces, dipole polarization relaxation triggered by atomic defects, and optimized magnetic loss ability from well-dispersed metallic Co species. Benefiting from these advantages, the Co/MnO@NC composites demonstrate superior electromagnetic wave absorption performances, with a minimum reflection loss value of −61.37 dB at the thickness of 3.5 mm and effective frequency absorption bandwidth of 6.32 GHz, covering the full Ku-band. Furthermore, power loss density and radar cross-section simulations validate that the Co/MnO@NC ternary composites possess exceptional microwave signal attenuation abilities, with a maximum radar cross-section reduction value of up to 27.98 dBm2 at 0°. Such outstanding absorption properties exceed those of most currently reported ternary composites and exhibit significant potential to replace conventional ferromagnetic-based absorbers. This work offers a straightforward strategy to fabricate ternary composites with excellent electromagnetic wave attenuation properties and sheds novel insights into the dissipation mechanisms.