Magnetoelectric Coupling Effect Research Articles

Differential Configuration for Highly Sensitive DC Magnetic Field Sensing Based on Nonlinear Magnetoelectric Effect

In recent years, magnetic sensors based on the magnetoelectric (ME) coupling effect have made remarkable progress in the detection of an ac magnetic field, but the detection of the dc magnetic field is still a challenging issue. Therefore, our work aims to develop a highly sensitive device for measuring the dc magnetic field. The designed ME device is based on a pair of highly consistent ME sensors and an intelligent differential configuration. By applying a strong driving ac magnetic field, the even-order harmonic components of the output voltage can be eliminated, and the odd-order harmonic components are superimposed concurrently. Due to the high responsivity (149 mV/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{T}$ </tex-math></inline-formula> ) of the first harmonic component to the dc magnetic field, we obtained a low detection limit of 0.8 nT for the dc magnetic field. These results further advance the research of ME composites used in dc field detection. This ME device may play an important role in many fields of magnetic field detection, such as magnetic localization, magnetic navigation, and so on.

Spanning Fermi arcs in a two-dimensional magnet

The discovery of topological states of matter has led to a revolution in materials research. When external or intrinsic parameters break symmetries, global properties of topological materials change drastically. A paramount example is the emergence of Weyl nodes under broken inversion symmetry. While a rich variety of non-trivial quantum phases could in principle also originate from broken time-reversal symmetry, realizing systems that combine magnetism with complex topological properties is remarkably elusive. Here, we demonstrate that giant open Fermi arcs are created at the surface of ultrathin hybrid magnets where the Fermi-surface topology is substantially modified by hybridization with a heavy-metal substrate. The interplay between magnetism and topology allows us to control the shape and the location of the Fermi arcs by tuning the magnetization direction. The hybridization points in the Fermi surface can be attributed to a non-trivial mixed topology and induce hot-spots in the Berry curvature, dominating spin and charge transport as well as magneto-electric coupling effects.

Magnetodielectric effect and significant magnetoelectric coupling of Co3NiNb2O9 single crystal

A4B2O9 (A = Co, Fe, Mn, Ni, B = Nb, Ta) compounds with a corundum-type structure can host multiferroic phenomena and present magnetoelectric coupling to achieve manipulations of their ground states by external fields. High quality Ni-doped Co4Nb2O9 single crystals of Co3NiNb2O9 have been synthesized for the first time using optical floating zone technique. Co3NiNb2O9 exhibits an antiferromagnetic order at 32 K with an easy magnetization axis in the ab plane. Field-dependent magnetizations at 20 K along [100] and [120] directions have a slope change at 6 and 9 kOe, respectively, indicating a spin-flop transition or spin rotation in the ab plane. Temperature dependence of dielectric constants along [100] and [120] directions show a magnetic-field-induced peak near the antiferromagnetic transition, proving a sizable magnetodielectric effect. Pyroelectric currents along [100] and [120] directions also have a divergent behavior near the transition under magnetic fields, manifesting a magnetoelectric coupling effect. The electric polarization along [120] direction reaches 128 μC/m2 under a magnetic field of 40 kOe, larger than that in most phases of the A4B2O9 system.

Tailoring skyrmion motion dynamics via magnetoelectric coupling: Toward highly energy-efficient and reliable non-volatile memory applications

Owing to the intriguing physical properties and significant spintronic applications, magnetic skyrmions have recently drawn intensive attention. Particularly, the skyrmion-based non-volatile memory (Sky-NVM) devices promise to be spintronic building blocks with high efficiency. However, tailoring Sky-NVM to achieve an energy-efficient and reliable operation in a synthetic, CMOS compatible, and magnetic-field-free integration is a challenging issue. Here, we report a new type of compact Sky-NVM with tailored skyrmion motion dynamics via in-plane strain gradient engineering. The skyrmion motion is merely driven by an in-plane electric field utilizing the magnetoelectric coupling effect, and the programmable switching is realized by gate biasing the potential barrier height via a voltage-controlled magnetic anisotropy. The proposed device is CMOS process compatible, and the comprehensive micromagnetic simulation results demonstrate that by applying a 0.3 V in-plane voltage combined with −0.17 V gate voltage, its write latency and the energy consumption reach 5.85 ns and 4.77 aJ/bit, respectively, superior to the state-of-the-art counterparts. Our work paves a new path toward ultra-low-power spintronic memory devices.

Ferroelectric control of band alignments and magnetic properties in the two-dimensional multiferroic VSe2/In2Se3

Our first-principles evidence shows that the two-dimensional (2D) multiferroic VSe2/In2Se3 experiences continuous change of electronic structures, i.e. with the change of the ferroelectric (FE) polarization of In2Se3, the heterostructure can possess type-I, -II, and -III band alignments. When the FE polarization points from In2Se3 to VSe2, the heterostructure has a type-III band alignment, and the charge transfer from In2Se3 into VSe2 induces half-metallicity. With reversal of the FE polarization, the heterostructure enters the type-I band alignment, and the spin-polarized current is turned off. When the In2Se3 is depolarized, the heterostructure has a type-II band alignment. In addition, influence of the FE polarization on magnetism and magnetic anisotropy energy of VSe2 was also analyzed, through which we reveal the interfacial magnetoelectric coupling effects. Our investigation about VSe2/In2Se3 predicts its wide applications in the fields of both 2D spintronics and multiferroics.

Tunning magnetism and anisotropy by ferroelectric polarization in 2D van der Waals multiferroic heterostructures

Since the successful exfoliation of two-dimensional (2D) magnetic CrI3 film, an increasing interest of research is the 2D analog of fascinating physical property of 3D material, of which the most attractive for both fundamental research and practical applications is the achieving effective magnetoelectric coupling and manipulation in 2D van der Waals (vdW) multiferroic heterostructure (HS). Herein, we report the discovery of ferroelectrically tunable orbital reconstruction in α-RuCl3/CuInP2S6 2D vdW HSs, enabling the remarkable transitions of magnetic ordering from proximate quantum spin-liquid state to ferromagnetic as well as the easy magnetization axis tuning from in-plane to out-of-plane direction. In addition, Monte Carlo simulation verified that, α-RuCl3 would transform into a perpendicular ferromagnetic material with Curie temperature of 89 K when the ferroelectric polarization points to α-RuCl3. Furthermore, by analyzing the density of states and the d-orbital-resolved magnetocrystalline anisotropy energy (MAE) of Ru atoms based on the second-order perturbation theory we elucidate that the contribution to MAE from the spin-orbit coupling interaction between d orbitals of Ru atoms show a transition from positive to negative, and ultimately dominating the MAE variation from easy-plane to easy-axis magnetization upon the reversible FE polarization. Therefore, the CuInP2S6 nonvolatile ferroelectric switching enables the nonvolatile electrical control of magnetic ordering and anisotropy. This work paves the way for exploring high-efficiency nanodevices and nonvolatile information storage based on the multiferroic 2D vdW HSs.

Direct evidence of mutual control of ferroelectric polarization and magnetization in Y-type hexaferrite BaSrCo2Fe12-Al O22 ceramics

Hexaferrites that exhibit the intrinsic and strong magnetoelectric (ME) coupling effect have been considered the most promising candidate for single-phase multiferroics. Currently, the strong ME coupling effect in this system was widely reported in single crystal form, while it is rare in polycrystalline one. In this work, Y-type hexaferrite BaSrCo2Fe12-xAlxO22 (x = 0.0, 0.3, 0.6 and 0.9) ceramics were manufactured with conventional solid-state reaction. Their magnetic, dielectric, and ME coupling properties were systematically surveyed. It was revealed that Al doping could result in a high magnetic transition temperature of ~ 345 K for x = 0.9. Also, the ferroelectric polarization and abnormal magnetodielectric properties were significantly enhanced which could be maintained down to 200 K. Most interestingly, the sample x = 0.9 displayed strong direct and converse ME coefficients of ~ 400 ps/m and ~ 900 ps/m at 150 K, respectively. Therefore, these results reveal that Al doping can broaden our understanding of the Y-type hexaferrite in room-temperature multiferroics.

Spin dynamics, critical scattering and magnetoelectric coupling mechanism of Mn4Nb2O9

The spin dynamics of Mn4Nb2O9 were studied using inelastic neutron scattering. A dynamic model is proposed to explain the observed spin-wave excitation spectrum from Mn4Nb2O9. The model indicates that the exchange interactions along the chain direction are weakly ferromagnetic while the exchange interactions between the neighbour chains are strongly antiferromagnetic. The antiferromagnetic interactions on the two MnO6 octahedron networks are dominant in the spin dynamics of this compound. A spin gap of about 1.4 meV was observed at the zone centre, which is attributed to the weak easy-axis magnetic anisotropy of Mn2+ ions. Magnetic critical scattering from Mn4Nb2O9 was studied in the vicinity of its Néel temperature T N as well, indicating homogeneous development of magnetic correlations. According to the symmetry analysis and its magnetic structure, the weak magnetoelectric coupling effect in Mn4Nb2O9 is ascribed to the uncancelled exchange striction on the two non-equivalent Mn2+ sites.

LaBr2 bilayer multiferroic moiré superlattice with robust magnetoelectric coupling and magnetic bimerons

Two-dimensional (2D) van der Waals (vdW) materials provide the versatile playground to stack two or more vdW layers for creation of superior materials with desired properties. Here we theoretically adopt a twisted stack-engineering of two LaBr2 monolayers to break space inversion symmetry for ferroelectricity and ultimately multiferroism. The enhancement and reversal of electric polarization are accompanied with the transition from interlayer ferromagnetic and antiferromagnetic orderings, demonstrating an effective magnetoelectric coupling effect with a mechanism dissimilar to that of the conventional multiferroics. Magnetization dynamics simulations show that such magnetic phase transition can excite topologically protected bimeron, and the skyrmion Hall effect can be suppressed by bilayer-bimeron stabilized in both ferromagnetic and antiferromagnetic configurations. Moreover, in the small-angle twisted moiré superlattice, the uniform polarization will evolve into a staggered domain structure, accompanied with the appearance of bimeron, which forms a significant discrepancy with the non-twisted stack-engineered multiferroic LaBr2 bilayer. This work provides a strategy for 2D multiferroic materials by twisted stack engineering of magnetic single layers.

FEM modelling of magnetoelectric coupling in (2-2)LSMO/ P(VDF-TrFE) polymer composite

Strain mediated magnetoelectric (ME) coupling effect has been investigated in bilayer structure of LSMO/P (VDF-TrFE) nanocomposite in the transverse ME mode. In the transverse mode, Finite Element Method (FEM) based small signal analysis has been performed by the COMSOL Multiphysics 6.0 software. La0.7Sr0.3MnO3(LSMO)/P (VDF-TrFE) nanocomposite (2-2) has been prepared by gluing LSMO pellet with P(VDF-TrFE) polymer film. This bilayer structure shows multiferroic property at room temperature. Simulated FEM modelverifies the magneto-strictive property of LSMO layer and explained the experimental results.Experimental and simulated ME coupling coefficient are found to be very close to each other.

Size-dependent and nonlinear magneto-mechanical coupling characteristics analysis for extensional vibration of composite multiferroic piezoelectric semiconductor nanoharvester with surface effect

We study the extensional vibration of composite multiferroic piezoelectric semiconductor (PS) nanoharvester driven via a time-harmonic magnetic field. A theoretical analysis about working performances of device is performed based on zero-order plate equations with surface and nonlocal effects, consisting of a nonlinear magneto-mechanical coupling constitutive model for giant magnetostrictive material Terfenol-D and a linear phenomenological theory of PS material ZnO. Numerical results indicate that the basic bahaviors (including resonant frequency, bandwidth characteristic, magneto-electric (ME) coupling effect, output power and energy conversion efficiency) of the nanoharvester, can be dramatically improved through circuit types, semiconduction, external magnetic field, pre-stress and surface effect. This work is essential and crucial for understanding the size-dependent and nonlinear mechanical behaviors of multiferroic PS nanodevices under the extremely complex magnetic field and pre-stress field environments.

Strain assisted magnetoelectric coupling in ordered nanomagnets of CoFe2O4/SrRuO3/(Pb(Mg1/3Nb2/3)O3–PbTiO3) heterostructures

We have explored the electric field controlled magnetization in the nanodot CoFe2O4/SrRuO3/PMN-PT (CFO/SRO/PMN-PT) heterostructures. Ordered ferromagnetic CFO nanodots (∼300 nm lateral dimension) are developed on the PMN-PT substrate (ferroelectric as well as piezoelectric) using a nanostencil-mask pattering method during pulsed laser deposition. The nanostructures reveal electric field induced magnetization reversal in the single domain CFO nanodots through transfer of piezostrains from the piezoelectric PMN-PT substrate to the CFO. Further, electric field modulated spin structure of CFO nanomagnets is analyzed by using x-ray magnetic circular dichroism (XMCD). The XMCD analysis reveals cations (Fe3+/Co2+) redistribution on the octahedral and tetrahedral site in the electric field poled CFO nanodots, establishing the strain induced magneto-electric coupling effects. The CFO/SRO/PMN-PT nanodots structure demonstrate multilevel switching of ME coupling coefficient (α) by applying selective positive and negative electric fields in a non-volatile manner. The retention of two stable states of α is illustrated for ∼106 seconds, which can be employed to store the digital data in non-volatile memory devices. Thus the voltage controlled magnetization in the nanodot structures leads a path towards the invention of energy efficient high-density memory devices.

Magnetoelectric dissociation of Alzheimer's β-amyloid aggregates.

The abnormal self-assembly of β-amyloid (Aβ) peptides and their deposition in the brain is a major pathological feature of Alzheimer’s disease (AD), the most prevalent chronic neurodegenerative disease affecting nearly 50 million people worldwide. Here, we report a newly discovered function of magnetoelectric nanomaterials for the dissociation of highly stable Aβ aggregates under low-frequency magnetic field. We synthesized magnetoelectric BiFeO3-coated CoFe2O4 (BCFO) nanoparticles, which emit excited charge carriers in response to low-frequency magnetic field without generating heat. We demonstrated that the magnetoelectric coupling effect of BCFO nanoparticles successfully dissociates Aβ aggregates via water and dissolved oxygen molecules. Our cytotoxicity evaluation confirmed the alleviating effect of magnetoelectrically excited BCFO nanoparticles on Aβ-associated toxicity. We found high efficacy of BCFO nanoparticles for the clearance of microsized Aβ plaques in ex vivo brain tissues of an AD mouse model. This study shows the potential of magnetoelectric materials for future AD treatment using magnetic field.

Tuning ferroelectrics to antiferroelectrics in multiferroic LaxSr1−xFe12O19 ceramics

The combination of antiferroelectricity (AFE) and ferromagnetism (FM) in one structure would allow the development of new type of multiferroic candidates, which be applicable not only in magnetoelectric memories but also in novel energy storage devices. Here we propose a novel type of multiferroic candidate LaxSr1-xFe12O19, whose room temperature state could betuned from ferroelectrics (FE) to antiferroelectrics by changing x from 0 to 0.5. The emphasis of this paper will be focused on the La0.5Sr0.5Fe12O19 system, in which full AFE and FM coexist. The pure antiferroelectric behavior in La0.5Sr0.5Fe12O19 ceramics is demonstrated by double polarization-electric field (P-E) hysteresis loops, which are fully separated by a linear antiferroelectric AFE component with zero net polarization. The material of La0.2Sr0.7Fe12O19 with the intermediate composition exhibits a hybrid ferroelectric/antiferroelectric state. The recoverable energy density of the antiferroelectric La0.5Sr0.5Fe12O19 phase reaches 14.3 J/cm3. This material demonstrates strong magnetoelectric coupling and giant magnetoresistance (GMR) effect. A 1.1T magnetic field generates electronic polarization up to 0.95uC/cm2, reduce the resistance by 117%, enhances dielectric constants by 540% and right shifts the maximum dielectric loss peak by 208 kHz. The combined functional responses provide an opportunity to develop novel multifunctional electric and energy storage devices.

Polarization-induced efficient charge separation in an electromagnetic coupling MOF for enhancing CO2 photocatalytic reduction

Rapid recombination of photogenerated carriers severely impairs the performance of photocatalysts, while polarization is an effective driving force for increasing the charge separation and hence improving the photocatalytic activity. In this work, a series of magnetoelectric-coupled layered metal–organic framework (MOF) catalysts with different Co-doped contents (denoted as Ni-MOF and CoxNi1-x-MOF) are fabricated with different polarities and employed as novel photocatalysts for CO2 photocatalytic reduction reaction. Our experiments show that the highest charge separation efficiency occurs in the Co0.1Ni0.9-MOF sample which has a maximal polarization. This Co0.1Ni0.9-MOF material has a best CO2 reduction performance of 38.74 μmol g−1h−1 which is at a high level in the currently reported layered materials. Meanwhile, it is found that a series of CoxNi1-x-MOF samples all display selectivity close to 100% for CO2 reduction to CO, which is desirable for industrial applications. Theoretical analysis shows that Co doping alters the degree of distortion of the asymmetrical Ni-centered octahedron {NiN2O4} in Ni-MOF by replacing Ni due to the magnetoelectric coupling effect and Jahn-Teller effect, which results in adjustable polarity of CoxNi1-x-MOF. This work provides new insights on how to improve photogenerated charge separation in MOF by enhancing polarization.

Atomic scale insights on the growth of BiFeO3 nanoparticles

This study provides new insights on the formation of the nanocrystallites of phase pure BiFeO3 prepared using sol–gel method with tartaric acid as the fuel as comprehended based on the local structure and magnetic hyperfine fields at Fe sites using Mossbauer spectroscopy. Important steps involved in the growth of the nanocrystallites of BiFeO3 in the sol–gel reaction are elucidated in a detailed manner in this study for the first time. Three important stages with the second stage marked by the formation of as high as 75% of nanocrystallites of BiFeO3 occurring over a narrow calcination temperature interval 700–723 K have been deduced in this study. Variation of hyperfine parameters with calcination temperature of the dried precursor gel leading to an increase in the mean size of crystallites of BiFeO3 has been deduced. The nanoparticles of BiFeO3 are deduced to exhibit weak ferromagnetic property in addition to being strongly ferroelectric based on the magnetization and P-E loop studies. Consequently an appreciable magneto electric coupling effect in terms of significant changes in P-E loop variation with the application of external magnetic field is elucidated in this study, which is comprehended based on the defects associated with BiFeO3 nanoparticles.

Enhanced dielectric, ferroelectric, and ferromagnetic properties of 0.7Bi1−xTmxFeO3–0.3BaTiO3 ceramics by Tm-induced structural modification

In this study, Tm-doped 0.7Bi1−xTmxFeO3–0.3BaTiO3 (x = 0–0.05) ceramics have been fabricated using traditional solid-phase reactions and their structural, morphological, and dielectric as well as multiferroic properties are investigated. X-ray diffraction and Rietveld refinement indicated the formation of a Tm-modulated morphotropic phase boundary (MPB) from the rhombohedral (R3c) and tetragonal (P4mm) phases to a single P4mm phase for Tm content of x = 0.02–0.03. Tm occupation of lattice sites is strongly suggested at both the A and B sites in the ABO3-type perovskite structure, which is supported by the obtained Raman spectra, the calculated tolerance factor, and dielectric relaxation characteristics. With the Tm-induced aforementioned–structural modification, the dielectric constant, remnant polarization (Pr), and remnant magnetization (Mr) values indicate that the dielectric and multiferroic properties are greatly improved. The obtained maximum remnant polarization (2Pr = 35.28 μC/cm2) and remnant magnetization (2Mr = 0.56 emu/g) are approximately two and seven times larger, respectively, than those of the sample without Tm substitution (x = 0). With increasing the Tm content, the remnant polarization, and the remnant magnetization exhibit almost the same trends in variation, indicating the possible existence of a relatively strong magnetoelectric coupling effect. Our study may provide a substitution strategy (structural modification by substituting the same element into two different lattice sites) to efficiently enhance the dielectric and multiferroic properties of BiFeO3–BaTiO3-based ceramics.

Strain-Induced Magnetoelectric Coupling in Fe3O4/BaTiO3 Nanopillar Composites.

Magnetoelectric coupling properties are limited to the substrate clamping effect in traditional ferroelectric/ferromagnetic heterostructures. Here, Fe3O4/BaTiO3 nanopillar composites are successfully constructed. The well-ordered BaTiO3 nanopillar arrays are prepared through template-assisted pulsed laser deposition. The Fe3O4 layer is coated on BaTiO3 nanopillar arrays by atomic layer deposition. The nanopillar arrays and heterostructure are confirmed by scanning electron microscopy and transmission electron microscopy. A large thermally driven magnetoelectric coupling coefficient of 395 Oe °C-1 near the phase transition of BaTiO3 (orthorhombic to rhombohedral) is obtained, indicating a strong strain-induced magnetoelectric coupling effect. The enhanced magnetoelectric coupling effect originated from the reduced substrate clamping effect and increased the interface area in nanopillar structures. This work opens a door toward cutting-edge potential applications in spintronic devices.

Magnetoelectric properties of three-layered composite thin film fabricated by pulsed laser deposition

Magnetostriction-piezoelectric composite films present promising application prospects due to the presence of the magnetoelectric effect. In this paper, a sandwich structure Bi4Ti3O12/CoFe2O4/Bi4Ti3O12 composite film was prepared in a pulsed laser deposition system. The morphology, EDX, XPS, ferroelectric, piezoelectric, ferromagnetic and magnetoelectric properties were investigated in detail. In the sample, the atomic percentages of Bi, Ti and O elements measured by EDX are 35.373%, 12.824% and 46.578%, respectively. The out-of-plane electric domain structure and the in-plane magnetic domain structure show that BTO and CFO phases have excellent ferroelectricity (Pr = 1.57 μC/cm−2) and ferromagnetism (Mr = 104.83 emu/cc), respectively. The piezoelectric properties are proportional to the ferroelectric properties, so the composite thin films also have good piezoelectric properties (d33max = 192 p.m./v). Moreover, a great magnetoelectric coupling coefficient (∼11.95 mV/cm·Oe) was obtained by mechanical strain transfer and interface coupling. By adding a ferroelectric layer to the composite thin film, the clamping effect can be reduced and the coupling between the ferroelectric and the ferromagnetic layers can be increased, providing the experimental basis for the research of magnetoelectric coupling effect.

Successive electric polarization transitions induced by high magnetic field in the single-crystal antiferromagnet Co2Mo3O8

The polar antiferromagnet ${\mathrm{Co}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ was recently reported as a new multiferroic material exhibiting remarkable second-order magnetoelectric (ME) coupling effect while no other metamagnetic transitions occurred at low magnetic field. Herein, we have investigated the ME phenomena under high magnetic field (up to 60 T) in ${\mathrm{Co}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ single crystals and observed unique ME response associated with the changes in the hidden magnetic moment on the honeycomb lattice. Two spin-flop transitions are unambiguously defined at ${H}_{c1}\ensuremath{\sim}27\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ and ${H}_{c2}\ensuremath{\sim}31\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ under $H$ along the $c$ axis at 1.7 K, accompanied by two successive colossal changes of electric polarization. The results on the anisotropy of magnetoelectricity as well as the angular-dependent polarization are well consistent with the ME tensor prediction, providing a better approach to understand the evolution of magnetic structures under high magnetic field. Therefore, the hidden magnetic transitions and distinctive magnetoelectricity provide a unique platform on which the ME coupling mechanism in the presence of rich magnetic phase transitions can be explored in this 238 family.