Large Magnetoelectric Research Articles

Magnetoelectric effects in ferromagnetic metal monolayers

Manipulating magnetic properties by purely electrical means is a key challenge to improve information technology. In the three-dimensional ferromagnetic (FM) metal thin films, for example, the 3d-transitonal metal thin films Fe, Co, and Ni, the electric-field effect is restricted within the surface around 2–3 Å due to the screening effect, and it is hard to separate the bulk and surface states. In the present investigation, through first-principles calculations, we explore the electric-field effect on the two-dimensional (2D) FM metal monolayers Fe3GeTe2, Fe3GeSe2, and Fe3GeTeSe. It is found that magnetic anisotropy energy (MAE) of these three materials follows the sequence: Fe3GeTe2 > Fe3GeTeSe > Fe3GeSe2, because the atomic spin–orbital coupling of Te is much stronger than that of Se. The most interesting finding is that the electric-field effect on MAE is obviously enhanced in Fe3GeTeSe, which is nearly ten times of Fe3GeTe2 and Fe3GeSe2, and we find the large difference results from its asymmetric structure. Our investigation reveals the magnetoelectric (ME) mechanism and obtains the large ME effect, which is of great significance in the 2D magnetoelectronics.

Tunable self-biased magnetoelectric effect in magnetization-graded magnetoelectric composites

Magnetoelectric (ME) composites, which are magnetostrictive-piezoelectric composites, have garnered attention for use in various application fields owing to their large ME coupling compared with single-phase multiferroic materials. The maximum ME coupling is observed when an increased DC magnetic bias field is applied, which results in large devices with degraded sensitivity due to electromagnetic noise. To address this problem, a strong self-biased ME composite that generates the maximum ME response in a zero-bias field was proposed in this study. Highly self-biased ME composites were prepared by combining soft magnetic Ni and highly permeable Metglas magnetostrictive layers with a Pb(Mg1/3Nb2/3)O3–PbZrTiO3 piezoelectric single-crystal laminate structure and inducing a magnetization gradient. The maximum ME voltage value without a DC bias field was evaluated to be 4.2 V/cm∙Oe for an MMNPNMM (M: Metglas foil, N: nickel, P: PMN-PZT) structure, which is 625 % higher than that of conventional ME composites. Therefore, the relatively bulky means of the DC-bias application on ME materials could be eliminated, resulting in a simple ME device with a small volume using the magnetization gradient concept.

Mg doping enhanced magnetoelectric effect in the polar magnet Fe2Mo3O8

Magnetoelectric (ME) effect has given rise to a new design principle for novel low-power electronic devices. The polar magnet ${\mathrm{Fe}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ with linear ME effect is one of the promising candidates. Unfortunately, for this material, a large ME response only appears in the ferrimagnetic state, which needs a high magnetic field to be activated. In this work, we successfully synthesize single-crystal ${({\mathrm{Fe}}_{0.95}{\mathrm{Mg}}_{0.05})}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ (FMMO), which achieves a linear ME effect in the antiferromagnetic ground state and shows a significantly improved ME coefficient in the ferrimagnetic state. Compared with the parent phase, six times linear ME coefficient and more than ten orders of magnitude second-order ME coefficient are accomplished in the FMMO. The spin-lattice coupling and the exchange-striction mechanism are believed to play a crucial role in creating the giant ME effect. The present study provides an idea for designing materials with strong ME coupling.

Large magnetoelectric effect in BaFe12O19-(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 particulate composite

Multiferroic composites with a large magnetoelectric response are gaining attractive interests for the design of magnetoelectric (ME) functional devices. In this work, the particulate ME composites (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3–xBaFe12O19 (x=0, 0.1, 0.2, 0.3, 0.4 and 1) were prepared, and their structural, dielectric, magnetic, ferroelectric, piezoelectric properties and magnetoelectric coupling were systematically investigated. The composites consisted of only two chemically separated phases with well-bonded interface. Dielectric and impedance analyses indicated the co-contribution of grain and grain boundary to polarization. Well-saturated ferroelectric and magnetic hysteresis loops demonstrated multiferroic nature. ME response was investigated elaborately by employing magnetically induced polarization, together with measuring ME voltage coefficient and magnetodielectric value. Specifically, a large ME coefficient of 26.78 ​mV/cm·Oe was achieved for x=0.3, which is higher than that in single-phase BaFe12O19 and its coupled composites.

Anisotropic magnetoelectric effect in lead zirconate titanate and magnetostrictive fiber composite structures

Objectives. The development of composite structures in which a strongly anisotropic magnetoelectric (ME) effect is observed is relevant for the creation of sensors that are sensitive to the direction of the magnetic field. Such an ME effect can arise due to the anisotropy of both the magnetic and the piezoelectric layers. In this work, a new anisotropic material named as a magnetostrictive fiber composite (MFC), comprising a set of nickel wires placed closely parallel to each other in one layer and immersed in a polymer matrix, is manufactured and studied. The study aimed to investigate the linear ME effect in a structure comprising of a new magnetic material, MFC, and lead zirconate titanate (PZT-19).Methods. The magnetostriction for the MFC structure was measured using the strain-gauge method; the ME effect was determined by low-frequency magnetic field modulation.Results. Structures with nickel wire diameters of 100, 150, and 200 μm were fabricated. The MFC magnetostriction field dependences were determined along with the frequency-, field-, and amplitude dependences of the ME voltage in the case of linear ME effect. Measurements were carried out at various values of the angle between the direction of the magnetic field and the wires. All samples demonstrated strong anisotropy with respect to the direction of the magnetic field. When the magnetic field orientation changes from parallel to perpendicular with respect to the nickel wire axes, the ME voltage decreases from its maximum value to zero.Conclusions. The largest ME coefficient 1.71 V/(Oe · cm) was obtained for a structure made of MFC with a wire diameter of 150 μm. With increasing wire diameter, the resonance frequency increases from 3.5 to 6.5 kHz. The magnetostriction of the MFC is comparable in magnitude to that of a nickel plate having the same thickness.

Domain-wall-induced electromagnons in multiferroics

Using an atomistic approach, we predict the emergence of hybrid quasiparticles, namely, domain-wall-induced electromagnons, that arise from dynamical couplings between magnons and optical phonons in systems possessing ferroelectric domain walls. These quasiparticles induce THz resonances in magnetoelectric responses and preferentially localize either near the domain walls or near the middle of domains. Such behavior is explained through dispersion analysis that allows us to track the emergent multidomain excitations back to single-domain magnetoelectric (ME) modes. The latter, scattered by a periodic array of domain walls, are shown to endow the domain-wall-induced electromagnons with a mixed localized mode and standing- or propagating-wave characters. Such features can be exploited to reach strikingly large ME conversion and design more reliable and ultrafast ME devices with less energy consumption and using, e.g., local probes.

Resonant Magnetoelectric Effect at Low Frequencies in Layered Polymeric Cantilevers Containing a Magnetoactive Elastomer

In this work, the resonance enhancement of magnetoelectric (ME) coupling at the two lowest bending resonance frequencies was investigated in layered cantilever structures comprising a magnetoactive elastomer (MAE) slab and a commercially available piezoelectric polymer multilayer. A cantilever was fixed at one end in the horizontal plane and the magnetic field was applied horizontally. Five composite structures, each containing an MAE layer of different thicknesses from 0.85 to 4 mm, were fabricated. The fundamental bending resonance frequency in the absence of a magnetic field varied between roughly 23 and 55 Hz. It decreased with the increasing thickness of the MAE layer, which was explained by a simple theory. The largest ME voltage coefficient of about 7.85 V/A was measured in a sample where the thickness of the MAE layer was ≈2 mm. A significant increase in the bending resonance frequencies in the applied DC magnetic field of 240 kA/m up to 200% was observed. The results were compared with alternative designs for layered multiferroic structures. Directions for future research were also discussed.

Observation of Spin‐Induced Ferroelectricity in a Layered van der Waals Antiferromagnet CuCrP2S6

AbstractCuCrP2S6, a van der Waals magnet having stacked layers of 2D honeycomb lattice made of CuS3 triangles and CrS6 octahedra, exhibits an A‐type antiferromagnetic order with the Néel temperature (TN) = 32 K. Upon in‐plane magnetic field (H) being applied below TN, H‐induced modulation of the c*‐axis electric polarization (ΔPc*) is found at fields lower than the saturation field µ0HS = 6.1 T, at which a forced ferromagnetic alignment sets in. Based on the symmetry analyses and dependence of ΔPc* on H and the azimuthal angle of applied H direction, a microscopic origin of the magnetoelectric (ME) coupling is attributed to the spin‐direction‐dependent p–d hybridization that is allowed due to the presence of off‐centered Cr3+ octahedra. A comparative study on CuCrP2Se6, however, finds no H‐induced P modulation due to cancellation of P between neighboring layers with the doubling of a crystallographic unit cell at TN. As the p–d hybridization mechanism allows generation of P in a single Cr atom–ligand pair, the results imply that large ME coupling should exist even in a single layer limit of CuCrP2S6.

Room-temperature large magnetoelectricity in a transition metal doped ferroelectric perovskite

There is increasing interest in novel magnetoelectric (ME) materials that exhibit robust ME coupling at room temperature (RT) for advanced memory, energy, spintronics, and other multifunctional device applications, by making use of the ability to control polarization with a magnetic field and/or magnetization via an electric field. Obtaining ME materials with strong ME coupling, understanding the origin, and manipulating its processing along with composition to realize large ME coefficients at RT constitute an important step in multiferroic research. To address this, we have investigated the multiferroic and ME properties of Ni-doped $\mathrm{Pb}({\mathrm{Zr}}_{0.20}{\mathrm{Ti}}_{0.80}){\mathrm{O}}_{3}$ (PZT). We find that the ferroelectric $({T}_{\mathrm{C}}\ensuremath{\sim}700\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ and weak ferromagnetic (\ensuremath{\sim}602 K) phase transitions of Ni-doped PZT are well above room temperature (RT), leading to a strong ME coupling coefficient (${\ensuremath{\alpha}}_{E,31}$) of $11.7\phantom{\rule{0.16em}{0ex}}\mathrm{mV}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{--1}\phantom{\rule{0.16em}{0ex}}{\mathrm{Oe}}^{--1}$ (${H}_{\mathrm{ac}}=1\phantom{\rule{0.16em}{0ex}}\mathrm{Oe}$ and $f=1\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$). While x-ray diffraction suggests a single-phase material, high-resolution transmission electron microscopy reveals regions with and without Ni present; thus magnetoelectric coupling between two phases is possible. First-principles calculations suggest the $(\mathrm{N}{\mathrm{i}}_{\mathrm{Pb}}{)}^{\ifmmode\times\else\texttimes\fi{}}$ defect is likely to be responsible for the experimental observed magnetism and ME coupling in Ni-doped PZT. We further demonstrate that Ni-doped PZT exhibits low loss tangent, low leakage current, large saturation polarization, and weak ferromagnetism. Ultimately, our work demonstrates that Ni-doped PZT is a cost-effective RT multiferroic with strong ME coupling.

Strain-Mediated Magneto-Electric Effects in Coaxial Nanofibers of Y/W-Type Hexagonal Ferrites and Ferroelectrics

Nanofibers of Y- or W-type hexagonal ferrites and core–shell fibers of hexagonal ferrites and ferroelectric lead zirconate titanate (PZT) or barium titanate (BTO) were synthesized by electrospinning. The fibers were found to be free of impurity phases, and the core–shell structure was confirmed by electron and scanning probe microscopy. The values of magnetization of pure hexagonal ferrite fibers compared well with bulk ferrite values. The coaxial fibers showed good ferroelectric polarization, with a maximum value of 0.85 μC/cm2 and 2.44 μC/cm2 for fibers with BTO core–Co2W shell and PZT core–Ni2Y shell structures, respectively. The magnetization, however, was much smaller than that for bulk hexaferrites. Magneto-electric (ME) coupling strength was characterized by measuring the ME voltage coefficient (MEVC) for magnetic field-assembled films of coaxial fibers. Among the fibers with Y-type, films with Zn2Y showed a higher MEVC than films with Ni2Y, and fibers with Co2W had a higher MEVC than that of those with Zn2W. The highest MEVC of 20.3 mV/cm Oe was measured for Co2W–PZT fibers. A very large ME response was measured in all of the films, even in the absence of an external magnetic bias field. The fibers studied here have the potential for use in magnetic sensors and high-frequency device applications.

Effects of post-annealing temperature and micropillar shape on physical properties of micropillar-type multiferroic composite thin films

Microplate (MP) and microrod (MR)-type CoFe2O4/(Bi3.25Nd0.65Eu0.10)Ti3O12 composite thin films were fabricated by a combination of reactive ion etching and metalorganic chemical vapor deposition. The effects of post-annealing temperature on the structural, magnetic, electrical, and magnetoelectric (ME) properties of the films were investigated. Based on the results, the optimal ferroelectric pillar structure to obtain a large ME voltage coefficient (α ME ) was determined. The electrical insulation properties for the films improved with increasing post-annealing temperature. On the other hand, magnetic and ferroelectric properties were degraded at high-temperature. Judging from the structural, magnetic, electric, and ME properties, the optimum post-annealing temperature was 700 °C. The shape of the ferroelectric layer had a significant influence on the ferroelectric properties and consequently on α ME . The MR shape exhibited a smaller clamping effect than the MP shape, producing a greater ME effect. The α ME for the MR-type film post-annealed at 700 °C was 5.5 mV cm−1 Oe−1.

Magnetoelectric coupling in micropatterned BaTiO3/CoFe2O4 epitaxial thin film structures: Augmentation and site-dependency

The prominent magnetoelectric (ME) effect in ME composites usually originates from an interfacial strain-mediated coupling between ferroelectric and ferromagnetic components. While ME composite bilayer thin films have been proposed for microdevice applications, the ME coupling is usually diminished because of the substrate clamping effect. Here, we apply simple CMOS/MEMS compatible top-down fabrication techniques to ferroelectric BaTiO3 (BTO) and ferromagnetic CoFe2O4 (CFO) bilayer epitaxial thin films to control the substrate clamping. We found augmented ME coupling in micro-patterned bilayer thin films compared to the as-deposited films due to the reduced substrate clamping. In addition, a site-dependent ME coupling within the microstructure was observed. Larger ME coupling was obtained near the edge of the microstructure, and site-dependent ferroelectric imprints were observed on the micropattern. This can be attributed to the non-uniform substrate clamping across the film, and the strain gradient developed in the BTO layer due to the magnetostriction of CFO. Our findings provide additional insights to the design of micro- and nanoscale devices based on 2–2 ME composite thin films.

Manipulation of microwave magnetism in flexible La0.7Sr0.3MnO3 film by deformable ionic gel gating

The flexible La0.7Sr0.3MnO3 (LSMO) film shows good mechanical stretchability and property stability under bending states, which makes it a candidate material for flexible electronics and spintronics devices. Here the microwave magnetism of flexible LSMO thin film has been manipulated effectively by the ionic gel (IG) gating process. A reversible and non-volatile magnetoelectric (ME) coefficient of 50 Oe/V was observed using electron paramagnetic resonance (ESR) technology at the flat multilayer structure. This ME coupling is caused by the electrons hopping between Mn3+ and Mn4+ ions under the interfacial electric double layer. When the membranes were bent to a radius of curvature of 15 mm, a larger ME coefficient of 67 Oe/V was also observed, which indicating that this flexible structure can work effectively under mechanical deformation. This work demonstrates the voltage control of magnetism for flexible correlated materials and paves a way towards wearable low-power devices based on flexible manganite films.

Antiferromagnetic-to-ferrimagnetic phase transition with large electric-polarization change in a frustrated polar magnet CaBaCo4O7

We investigate phase transitions of a geometrically frustrated polar magnet ${\mathrm{CaBaCo}}_{4}{\mathrm{O}}_{7}$, which exhibits the largest magnetoelectric (ME) effect in multiferroic compounds reported so far. Measurements of magnetization, sound velocity, and neutron diffraction of single crystals reveal an antiferromagnetic phase between the ferrimagnetic transition temperature ${T}_{\mathrm{C}}\ensuremath{\sim}60$ $\mathrm{K}$ and ${T}^{*}\ensuremath{\sim}69$ $\mathrm{K}$. In the antiferromagnetic phase, the ordered Co moments on the triangular layers remain nearly disordered. We demonstrate that a large electric-polarization change emerges upon the antiferromagnetic-to-ferrimagnetic transition. The large ME coupling can be attributed to the exchange striction.

Magnetoelectric materials and devices

Over the past few decades, magnetoelectric (ME) materials and devices have been investigated extensively, which is one of the most interesting research topics since the revival of multiferroic laminates with large ME coupling coefficients. The existence of two or more ferroic properties in the ME systems plays key roles in the next generation of novel multifunctional devices. Strong ME coupling has been demonstrated in various ME systems, including single-phase bulk or thin-film materials and bulk or thin-film composites such as piezoelectric/magnetostrictive heterostructures. Based on the coupling mechanisms, a variety of device applications have attracted ever-increasing attention, such as magnetic field sensors, voltage tunable inductors, mechanical ME antennas, which are compact, lightweight, and power-efficient. These novel ME materials and devices provide great opportunities for next-generation magnetic field sensing, communication systems, spintronics, nonvolatile memory applications, etc. In this paper, we try to summarize the most recent progress on ME materials, phenomena, and devices in the past few years, with emphasis on thin-film composite materials and devices. Some unsolved questions and future directions where the community could head for are also provided.

Enrichment of magnetoelectric effect in the hexagonal BaTi1-xCoxO3 artificial type-II multiferroics by defects

Artificial magnetoelectric material with enrichment of magnetoelectric (ME) coupling coefficient was achieved via mixed-oxide route in cobalt substituted BaTiO3 multiferroics. The observed large ME coupling coefficient induced by spin–orbit interaction through the symmetry breaking due to the off-stoichiometry oxygen. Structural details extracted from the Rietveld refinement indicate the rapid arrival of a single hexagonal phase (P63/mmc) at the expense of the tetragonal phase (P4mm) above x = 0.03. SAED patterns evidence to the structural coexistence, morphotropic phase boundary (MPB), (P4mm + P63/mmc) in x = 0.01 and 0.03 while hexagonal phase alone in x ≥ 0.05. Core-level XPS spectrum of Ba(3d), Ti (2p), Co (2p), O (1s) evidences the occurrence of the single oxidation state of Ba ion (Ba2+) and aliovalent of Ti (Ti4+ and Ti3+), Co (Co3+ and Co2+) and O (O2− and O1−) ions respectively. The weakening of ferroelectric loops arises from the formation of the non-ferroelectric hexagonal phase by the non-stoichiometric oxygen. For the first time, a high value of energy efficiency of 54.7% was achieved in the BaTi0.99Co0.01O3 sample. The ferromagnetism originated from the contributions of the super-exchange interaction of Co3+(octahedral)-O2−-Co3+(pentahedral) and double-exchange interaction (Co2+-O2−-Co3+) Among all the samples, an excellent magnetoelectric coupling coefficient (αME) value of 29.6 mV/cm Oe is attained in the hexagonal BaTi0.93Co0.07O3 sample.

Poly(vinylidene fluoride-trifluoroethylene)/cobalt ferrite composite films with a self-biased magnetoelectric effect for flexible AC magnetic sensors

With the rapid development of artificial intelligence and wearable devices, flexible magnetic sensors have attracted much attention in recent years. In this work, large self-biased 0–3 type poly(vinylidene fluoride-trifluoroethylene)/cobalt ferrite (P(VDF-TrFE)/CoFe2O4) flexible magnetoelectric (ME) composite films are proposed for the development of AC magnetic sensors. P(VDF-TrFE)/CoFe2O4 composite films with CoFe2O4 nanoparticle mass contents from 5 to 30% are successfully fabricated through the solution casting method. The results show that the nanoparticles are homogeneously dispersed in the P(VDF-TrFE) matrix, and the composite films have both excellent ferroelectric and ferromagnetic properties. The P(VDF-TrFE)/CoFe2O4 composite films all exhibit a large ME effect. The ME coefficient reaches 47.1 mV·cm−1·Oe−1 for the film with a CoFe2O4 nanoparticle mass content of 20% at resonance frequency. Moreover, the composite films have a large self-biased ME effect with a maximum value of 20.4 mV·cm−1·Oe−1, which is mainly due to the high remnant magnetization of CoFe2O4 nanoparticles. To evaluate the composite films for application in magnetic sensors, the response of the ME output voltage to an AC magnetic field without a bias DC magnetic field was measured. The good linear correlation coefficient, sensitivity and repeatability indicate that the proposed 0–3 type P(VDF-TrFE)/CoFe2O4 composite film is a promising material for flexible AC magnetic sensors.

Ultraflexible and Malleable Fe/BaTiO3 Multiferroic Heterostructures for Functional Devices

AbstractThe high demand for flexible spintronics based on multiferroic heterostructures makes growing high‐quality flexible, functional oxides urgently, in which needs to be deposited on lattice‐matched substrates. In this paper, ultraflexible and malleable iron (Fe)/BaTiO3 (BTO) multiferroic heterostructures are demonstrated, showing a perfect crystallinity and hetero‐epitaxial growth. In terms of performance, they indicate good multiferroic properties and excellent bending tunability, as well as obvious magnetoelectric (ME) coupling effect. During the phase transformation from the rhombohedral phase to the orthorhombic phase of BTO layers in the heating process, a large ME coupling coefficient of 120 Oe °C−1 along the out‐of‐plane direction is obtained. This value keeps consistent in the phase‐field simulation of magnetic domain evolution, in which the biaxial compressive strain induced‐magnetoelastic anisotropy facilitates the magnetic easy axis of Fe layers to the [110] or [–1–10] direction. Besides, ultraflexible Fe/BTO heterostructures are found to have a 690 Oe ferromagnetic resonance (FMR) field shift along the out‐of‐plane direction under the flexible tuning (R = 5 mm). This work should pave a way toward flexible spintronic and functional devices with fast speed, portability, and low energy consumption.

Evaluation of Metglas/polyvinylidene fluoride magnetoelectric bilayer composites for flexible in-plane resonant magnetic sensors

Flexible magnetic sensors are attracting more and more attention because of their application in wearable devices. In this paper, Metglas/polyvinylidene fluoride (PVDF) bilayer composite with good flexibility was fabricated to evaluate its applicability as a flexible in-plane magnetic sensor. The magnetoelectric (ME) coupling characteristics and sensing performance of the sample were investigated under different test conditions, including different AC and DC magnetic field, and changing the direction of the magnetic field and the bending degree of the sample. The sample shows a large ME coefficient with a value of 176.41 V cm−1 Oe. The sensitivity, linearity and deviation of the sample are 892.96 mV Oe−1, 0.99965 and ±2% for the AC magnetic field, and 157.6 mV Oe−1, 0.99444 and ±5% for the DC magnetic field, respectively, and it shows excellent stability over repetitions. Moreover, the sample was gradually rotated anticlockwise in the magnetic fields. The output voltage of the sample varies with the rotation angle and has a good symmetry in plane, which is described well by a sine function. In addition, the clamping effect of the sample was studied. Even when bent, the sample still maintains an excellent and stable performance. The sensitivity and linearity of the sample with a bent angle of 23.5° are 254.37 mV Oe−1 and 0.99975 for the AC magnetic field, and 28.07 mV Oe−1 and 0.99309 for the DC magnetic field, respectively. The deviation of measurements is small for both the AC and DC magnetic sensors. In summary, the present study shows that the Metglas/PVDF bilayer composite has a good sensing performance and is suitable for = flexible in-plane resonant magnetic sensors.

Dielectric and magnetoelectric properties of (BiBa)(FeTiZn) O3/CoFe2O4 lead-free particulate composites

The magnetic, dielectric, and magnetoelectric (ME) properties of particulate composites containing lead-free piezoelectric 0.97[0.67BiFeO3-0.33BaTiO3]-0.03Bi(Zn0.5Ti0.5) O3 (BF33BT-3BZT) and magnetostrictive CoFe2O4 (CFO); (100-x)[BF33BT-3BZT]-xCFO, x = 13, 25, 37, 47 mol%; have been investigated. The pure ferroelectric BF33BT-3BZT shows a non-dispersive and sharp phase transition, while the composites exhibit relaxor behavior which is described by Vogel - Fulcher law. The ME voltage coefficient is studied as a complex quantity and its dependence on magnetic field is discussed within the framework of dynamic magnetostriction. The composite with x = 37 shows the highest ME voltage coefficient of 5.7 mV/cm.Oe. The results show that, compared to cobalt ferrite, the composite of BF33BT-3BZT with nickel ferrite produces larger ME voltage at a lower magnetic field, confirming that the magnetic field dependence of magnetostriction has a crucial role on the ME properties of the studied multiferroic composites.