Magnetoelectric Voltage Research Articles

Effect of interface coupling on magnetoelectric response of Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3 thin film under different strain states

Epitaxial Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3 (PZT/LSMO) thin film grown on SrTiO3 single-crystal substrate has been fabricated by pulsed laser deposition. The results of X-ray diffraction and reciprocal space mapping indicate that PZT and LSMO are under different strain states, respectively. This configuration could enhance the interface coupling coefficient (k), resulting in an improvement of magnetoelectric voltage coefficient (αE31). The k value increases with the increase of DC magnetic field owing to the magnetostriction of ferromagnetic LSMO. The maximum αE31 reaches 122 mV/cm Oe at the DC magnetic field of about 4.5 kOe, which is in good agreement with the result of theoretical calculation. The understanding of the effect of interface coupling for ferroelectric/ferromagnetic composite thin film with different strain states could be useful for the design of multifunctional devices.

A hexagonal-framed magnetoelectric composite for magnetic vector measurement

In this work, a multi-terminal hexagonal-framed magnetoelectric composite (HFMEC) made of amorphous FeBSi alloy (Metglas) ribbons and three sandwiched [011]-oriented PMN-PT single-crystal fibers (Pb(Mg1/3Nb2/3)O3-PbTiO3) arranged with a 120° interval is presented, and the directional magnetoelectric (ME) effect of the HFMEC operating in the L-T mode under a constant-amplitude AC magnetic field is investigated. It is found that the HFMEC exhibits threefold symmetric directional ME coupling in response to an applied in-plane DC magnetic field HDC, while each ME terminal shows a twofold symmetry due to the magnetization and demagnetization effect of HDC. Moreover, a valid formula for calculating the angular direction of the magnetic field is also presented. It is further revealed that the HFMEC exhibits a “V” shaped ME voltage output as a response to HDC due to the geomagnetic field (HGeo) effect, and the knee point of the curve literally reveals the magnitude of local HGeo, while the direction of HDC indicates a reverse direction of HGeo. The proposed HFMEC provides a great potential for a vector magnetometer as well as geomagnetic sensor application.

Giant zero-biased flexible magnetoelectric laminate composites for wearable magnetic sensor

Flexible magnetoelectric (ME) laminate composites consist of polyvinylidene fluoride (PVDF) and nanocrystalline alloy (FeCuNbSiB) were prepared. The ME coupling properties under different bending angle (θ) at zero dc bias magnetic field (Hdc) were investigated. The experimental results demonstrate the optimum zero-biased resonant ME voltage coefficient (MEVC) of ME laminate composites can reach 17.65 V/(cm·Oe). This is mainly due to the large permeability and low saturation magnetostrictive coefficient of the nanocrystalline alloy. The induced zero-biased ME voltages of ME laminate composites show an excellent linear relationship to ac magnetic field at bending states over a wide range. This laminate composite shows promising applications for high-sensitivity and small-size wearable magnetic sensors without bias.

Theoretical and experimental analysis of temperature dependent nonlinear behaviour of tri-layered magnetoelectric composites

In this work, experiments have been performed to study the magneto-mechanical behaviour of (Tb0.3Dy0.7Fe2) under various operating temperatures. Based on the experimental results, a three dimensional nonlinear constitutive model under thermodynamic framework have been developed to capture the thermo-magneto-mechanically coupled behaviour. Then, the model parameters have been identified using least square approximation. Later, using the developed model, a homogenisation procedure has been introduced to simulate magnetoelectric (ME) coupling behaviour for various temperature and volume ratio of composition for different configurations (T-T, L-T, T-L, L-L) in layered ME composites. In a particular configuration (say L-T) is represented by referring first letter (L) as the direction of external magnetic field and the second letter (T) as the direction of polling in the piezoelectric material. Consequently, an experimental setup has been established to capture the ME voltage coefficient at L-T mode under different operating temperatures. Comparison between the experimental data and the simulation results shows good agreement with each other. Comparing the ME coupling behaviour for various configurations, L-L and L-T configurations are observed to have higher coupling factor.

Elastic and Anelastic Properties of a Particulate Magnetoelectric Composite (x)Mn0.4Zn0.6Fe2O4–(1 − x)PbZr0.53Ti0.47O3

Elastic (elastic compliance) and anelastic (internal friction) properties of a particulate magnetoelectric composite (x)Mn0.4Zn0.6Fe2O4–(1 − x)PbZr0.53Ti0.47O3 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.6) at a frequency of ≈30 Hz over a temperature range from 290 to 700 K are studied. Temperature dependences of elastic compliance and internal friction near the ferroelastic Curie point are found to be well approximated by power functions. Observed dependences of exponents on the composite composition are associated with the substitution of atoms in the PbZr0.53Ti0.47O3 lattice by atoms in the Mn0.4Zn0.6Fe2O4 lattice during the high‐temperature sintering of composite samples. A correlation is revealed between the transverse magnetoelectric voltage coefficient and smearing parameters of the ferroelastic phase transition.

Tutorial: Product properties in multiferroic nanocomposites

The coupling between magnetic and electric subsystems in composites of ferromagnetic and ferroelectric phases is a product property that is facilitated by mechanical strain that arises due to magnetostriction and the piezoelectric effect in the constituent phases. Such multiferroic composites are of immense interests for studies on the physics of electromagnetic coupling and for use in a variety of applications. Here, we focus on magneto-electric (ME) coupling in nanocomposites. Particular emphasis is on core-shell particles and coaxial fibers, thin film heterostructures, and planar structures with a variety of mechanical connectivity. A brief review of models that predict strong ME effects in nanostructures is followed by synthesis and characterization. Core-shell particulate composites can be prepared by hydrothermal processes and chemical or deoxyribonucleic acid-assisted assembly. Electrospinning techniques have been utilized to prepare defect free core-shell nanofibers. Core-shell particles and fibers can be assembled into superstructures with the aid of magnetic and electric fields and characterized for possible use in advanced technologies. Chemical-vapor deposition techniques have been shown to be effective for the preparation of heterostructures of ferrites and ferroelectrics. Exotic planar multiferroic structures with potential for enhancing ME coupling strengths are also considered. Scanning probe microscopy techniques are ideal for probing the nature of direct- and converse-ME coupling in individual nanostructures. Magnetoelectric characterization of assemblies of nanocomposites can be done by ME voltage coefficient, magnetic field induced polarization, and magneto-dielectric effects. We conclude with a brief discussion on possible avenues for strengthening the product properties in the nanocomposites.

Dynamic/static displacement sensor based on magnetoelectric composites

This study presents a dynamic/static displacement sensor based on both end fixed Terfenol-D/PZT (lead zirconate titanate) magnetoelectric composites. Owing to the fixed boundary condition, the magnetostriction of Terfenol-D under the magnetic field is limited and the stress acts on PZT through mechanical coupling, and finally, an induced voltage is generated due to the piezoelectric effect in PZT. The magnetic field applied on the magnetoelectric composites varies with the displacement of the permanent magnet which represents the displacement to be measured. In that case, the determination of displacement can be transformed into determining the variation of the magnetic field. The experimental results manifest that the frequency of magnetoelectric voltage is the same as the frequency of displacement. The dynamic displacement sensitivity of this sensor increases with the increase in the input frequency in the low frequency range and the decrease in the length of the air gap. The sensitivity is 6.549 mV/μm with a 0.75 mm air gap for dynamic displacement at 10 Hz and 0.84 μV/μm with a 2.5 mm air gap and an external magnetic field at 1 kHz for static displacement. It can be concluded that the displacement measuring mechanism based on the magnetoelectric effect is a promising robust and accurate method.

15-Mode piezoelectric composite and its application in a magnetoelectric laminate structure

Magnetoelectric composites have recently been attracting attention owing to their possible application in various advanced electronics. The piezoelectric material used in a magnetoelectric composite is an important determinant of the electrical performance of the device. In this study, we report on the fundamental characteristics and magnetoelectric application of a 15-mode piezoelectric composite. The centimeter-scale 15-mode piezoelectric composite implemented by a novel fabrication process exhibits successful 15-mode operation along with excellent piezoelectric properties d15 = 793 × 10−12 C N−1, g15 = 32 × 10−3 V m N−1, k15 = 0.62, and d15·g15 = 25376 × 10−15 m2 N−1. Magnetostrictive-piezoelectric laminate structures designed to generate shear stress were fabricated using the 15-mode piezoelectric composites, and their magnetoelectric characteristics were investigated systematically. A giant magnetoelectric voltage coefficient of 18.4 V cm−1 Oe−1 was obtained at a low frequency of 660 Hz from the laminate, indicating the potential of the 15-mode piezoelectric composite for application in high-performance magnetoelectric devices.

Enhanced magnetoelectric voltage in ferrite/PZT/ferrite composite for AC current sensor application

In this paper, we report the fabrication of a rare-earth free current sensor based on a PZT/NiCoZn-ferrite magnetoelectric (ME) trilayer composite disk. To improve the sensitivity of the sensor, the structure uses an in-plane series connection, which increases the ME voltage by two for a fixed volume. Then, we propose a full characterization of the sensor: electrical modeling, low and high frequency limits, sensitivity, linearity, distortion and resolution. The device is also evaluated under sinus, square, and triangle waveform currents, which are excitation signals commonly used in the field of electrical engineering. The current sensor shows high current sensitivity (90 mV/A), good linearity from 0.001 to 30 A and low added impedance (0.01 Ω) in a frequency range of 10 Hz–30 kHz for a very compact structure (4 cm3). It also exhibits a high resolution of 1 mA (for a 1 A peak signal) and good stability.

Tailored dielectric, magnetic and magnetoelectric properties of Cu0.6Zn0.4Fe2O4-BaTiO3 composites

The composites samples (1-x) (Cu0.6Zn0.4Fe2O4) CZF + x (BaTiO3) BT, where (x = 0%, 10%, 20%, 30%, 40%, 50% 60%, 70%, 80%, 90% and 100%), have been prepared by ball milling. The x-ray diffraction showed that two phases have retained their identity in the composites and no undesired reaction has occurred between two phases. The tetragonality factor (TF) of ferrimagnetic phase increases with BT content up to x = 30% and then decreases at x = 40% but, for higher BT content; TF is nearly constant. The AC resistivity enhances with BT content, showing semiconductor behavior. Furthermore, it is demonstrated that CZF enhances ferroelectricity of BT. In addition, the initial permeability of the samples decreases with BT content and increases with higher selected frequency. It is demonstrated that the magnetoelectric voltage coefficient (ΔE/ΔH) depends strongly on BT content. The maximum ΔE/ΔH of some CZF-BT composites is higher than reported values of other ferrite-BT composites indicating vital role of CZF in developing magnetoelectric effect for ferrite-BT composites.

Theory of magnetoelectric effects in multiferroic core–shell nanofibers of hexagonal ferrites and ferroelectrics

A model is developed for magnetoelectric (ME) interactions in coaxial nanofibers of hexagonal ferrites and ferroelectrics. Multiferroic nanocomposites with hexagonal ferrites are of interest for achieving strong ME coupling under zero external magnetic bias due to their high uniaxial or planar anisotropy fields. In this work we considered the ME coupling in core–shell fibers of lead zirconate titanate (PZT) and ferrimagnetic W- and Y-type hexagonal ferrites with high magnetostriction and piezomagnetic coupling. Modeling of the direct-ME effects, i.e. sample response to an applied magnetic field, is done in terms of the ME voltage coefficients (MEVCs) at low frequencies and at electromechanical resonance (EMR). The converse-ME effect, response of the fibers to an applied DC electric field, is considered at ferromagnetic resonance (FMR). Expressions have been obtained for MEVCs at low frequency and EMR, and for the converse-ME coefficient at FMR. The theory predicts strongest direct-ME coupling in fibers of Ni2Y-PZT and the weakest coupling in Zn2Y-PZT. The MEVC at EMR is one to two orders of magnitude higher than at low frequency and the peak MEVC remains the same for fibers of ferrite core-PZT shell as for PZT core-ferrite shell. The converse-ME effect is expected to be the strongest for fibers of Co2W-PZT and weakest in Ni2Y-PZT. The model has been extended to include an assembled array of core–shell fibers and weakening of the ME coupling is predicted in such arrays due to magnetic and electric dipole–dipole interactions. The theory presented here is of importance for self-biased sensors of low frequency and RF magnetic fields.

Magneto-electric coupling and improved dielectric constant of BaTiO3 and Fe-rich (Co0.7Fe2.3O4) ferrite nano-composites

(x)BaTiO3–(1−x)Co0.7Fe2.3O4 (BTO-CFO) magnetoelectric nanocomposite ceramic with x = 0.0, 0.25, 0.50, 0.75, 1.00 were successfully designed and fabricated by sol-gel route. The structural, micro structural, dielectric, ferromagnetic, ferroelectric and magnetoelectric properties of these composites were investigated. The coexistence of tetragonal phase and cubic spinel phase, without any secondary phase in composites is confirmed by the X-ray diffraction measurement. The field emission scanning electron micrograph show well distributed ferrite and ferromagnetic phases in the composites. The energy dispersive X-ray results revealed the purity and stoichiometry of BTO-CFO nanocomposites. The dielectric constant and loss factor of the composites were studied as a function of frequency. The composite sample with x = 0.50, results in higher value of dielectric constant whereas CFO possess lowest value of dielectric constant. The magnetization hysteresis (M−H) loop of the composites show ferromagnetic behavior with saturation magnetization values, Ms varies from 15 to 67.68 emu/g and coercive field Hc from 1538 to 1862 Oe. All the composites exhibit typical ferroelectric hysteresis loops indicating the presence of spontaneous polarization. The magnetoelectric voltage coefficient increases linearly with increases in applied d.c. magnetic bias field up to 8 KOe. The maximum value of magnetoelectric voltage coefficient, αME=7.7 mV/cm Oe for BTO-CFO composite having 25% ferrite and 75% ferroelectric content. The high ME voltage coefficient of BTO-CFO composite may be suitable for storage device application.

Multilayer multiferroic composites with imperfect interfaces

We study the macroscopic behaviors of multilayered multiferroic composites with interface imperfections by a direct micromechanical approach. Both generalized interface stress type and generalized linear spring type imperfect interfaces are considered. Concise matrix expressions of the overall behaviors of the layered piezoelectric–piezomagnetic composite with contact imperfection are presented. The key step is to observe that the two types of imperfect interface conditions are equivalent to the perfect ones due to the laminated geometry. Numerical calculations are demonstrated for BaTiO3–CoFe2O4 multilayer media, and are shown in good agreement with the more involved interphase model. Furthermore, it is observed that the interface imperfection would reduce the magnitude of the magnetoelectric voltage coefficients as compared to the corresponding perfect interface case. This feature is opposite to that predicted and observed in the corresponding cylindrical composites.

A quasistatic hysteresis model for magnetoelectric effect in multiferroic nanostructured films with surface effect

The investigation of hysteresis induced self-biased magnetoelectric (ME) coupling in multiferroic nanostructured films is significant for self-biased nano-devices. In this paper, we propose a quasistatic hysteresis model for ME effect in multiferroic nanostructured films based on surface stress model and multi-field coupled hysteretic constitutive model. For an asymmetric structure consisting of different magnetostrictive phases, the flexural strain is considered in the theoretical model. It is revealed that ME coupling in ME composites with nano-scale thickness is significantly size-dependent below critical size, which is enhanced by surface effect. Self-biased ME hysteretic behavior can be observed by considering the hysteretic effect of magnetostrictive materials, resulting in a large ME voltage coefficient in absence of bias magnetic field. The self-biased ME voltage coefficient is affected by pre-stress and thermal variation due to the complex magneto-elastic-thermal coupling characteristics of constituent materials. The proposed model provides a method to analyze and evaluate the nonlinear ME coupling characteristics of self-biased nano-devices operating under extreme stress or temperature conditions.

Studies on structural, dielectric, conductivity, magnetic and magneto-electric properties of barium titanate doped with lithium ferrite

In this paper, we report the synthesis of a multiferroic composite BaTiO3 (BT) doped with Li0.5Fe2.5O4 (LF) having chemical formulae (1-x) BaTiO3+ (x) Li0.5Fe2.5O4 (x = 0, 0.05, 0.1, 0.15) using conventional solid state reaction method. We have focused on the structural and multiferroic properties of LF doped BT. We have characterized the grown composites by XRD, FESEM with EDAX, Piezoelectric coefficient, dielectric studies, A.C conductivity studies, magnetic properties and magneto-electric (ME) voltage coefficient. The XRD studies reveal the tetragonal nature of all composites. We have calculated the lattice parameters and the crystallite size from XRD pattern. The XRD patterns of all composites exhibit diphasic nature. The dielectric constant of all composites decreases steeply with an increase in the frequency and attains a nearly constant value in the high-frequency region. The variation of conductivity with the frequency reveals that at high-frequency region, the maximum conductivity decreases with an increase in the % of LF. The variation of conductivity with temperature reveals that the Curie temperature of the composite decreases as and when the % of LF is increased in BT. We have also studied the temperature dependence of the magnetization and the variation of the magneto-electric voltage coefficient (ME) with a magnetic field. The transition temperature and Neel temperature of all composites increased with increase in LF. The Magneto-electric (ME) coefficient of composites decreased with increase LF content.

Magnetoelectric properties of 0.5BiFeO3–0.5Pb(Fe0.5Nb0.5)O3 solid solution

Magnetoelectrics are materials that join magnetic and electric orderings in the same phase. They exhibit magnetoelectric coupling which is important from the fundamental and practical point of view. The subject of the paper is a presentation of magnetic, electric and magnetoelectric properties of 0.5BiFeO3–0.5Pb(Fe0.5Nb0.5)O3 solid solution. The obtained material belongs to oxide perovskite magnetoelectrics of relatively high magnetic and electric ordering temperatures. Both temperatures are considerably above room what suggests potential application possibilities of the material. The magnetic properties were investigated using Mössbauer spectroscopy and magnetization measurements. The solid solution is an antiferromagnet with incomplete compensated magnetic moments. The electrical properties were determined using impedance spectroscopy analysis. There is an observed change of the electrical properties at the magnetic ordering temperature what indicates magnetoelectric coupling in the system. The electrical conductivity mechanism is also proposed. Magnetoelectric voltage coefficient was determined and possible explanation of its changes was proposed.

Diameter and sequence effects on magnetoelectric effect in FeCo/Pb(Zr,Ti)O3/Ni trilayered long cylindrical composite structures

Here we studied the magnetoelectric (ME) effect of FeCo/Pb(Zr,Ti)O3/Ni and Ni/Pb(Zr,Ti)O3/FeCo trilayered long cylindrical composites made up of negative magnetostrictive Ni layers, positive magnetostrictive FeCo layers and piezoelectric Pb(Zr,Ti)O3 (PZT) cylinders. Magnetostrictive layers were directly deposited on the PZT by electroless deposition. The bias magnetic field and the frequency dependences of ME effect were studied in both the axial and the vertical modes. The mean diameter of the trilayered long cylindrical composites has a strong impact on the ME effect. Keeping the height fixed, the resonant frequency and the maximum ME voltage coefficient decrease with the mean diameter of the cylinder increasing, while the optimal bias magnetic field HDC approximately remains constant. Besides, the ME effect is also influenced by the sequence of Ni and FeCo layers. The FeCo/Pb(Zr,Ti)O3/Ni cylinder obtains larger ME voltage coefficients, superior to those of the Ni/Pb(Zr,Ti)O3/FeCo in both modes. This work is significant for optimizing ME performance of the cylindrical layered ME composites in practical application such as magnetic field sensors and energy harvesters.

Thickness dependence of magnetoelectric properties for Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3 heterostructures

In this work, magnetoelectric thin film heterostructures of Pb(Zr0.52Ti0.48)O3/La0.67Sr0.33MnO3(PZT/LSMO) were epitaxially grown on SrTiO3(STO) substrates. aa-phase and r-phase in PZT layer could be observed simultaneously. Thickness dependent magnetoelectric effect of these heterostructures is investigated in detail. The results show that the r-phase in PZT layer will significantly improve the magnetoelectric voltage coefficient (αE31), and the amount of r-phase will decrease with increasing thickness of PZT layer. The maximum αE31 can reach 1153 mV/cm Oe for the sample with PZT thickness of 32 nm. This work will be of significance for tuning magnetoelectric effect via thickness ratio between ferroelectric and ferromagnetic layers.

Synthesis and study of structural, dielectric, magnetic and magnetoelectric properties of K0.5Na0.5NbO3–CoMn0.2Fe1.8O4 composites

Magnetoelectric (ME) composites consisting of K0.5Na0.5NbO3 (KNN) as ferroelectric phase and CoMn0.2Fe1.8O4 (CMFO) as ferrite phase with general formula (x) CoMn0.2Fe1.8O4–(1 − x) K0.5Na0.5NbO3 (x = 10, 20, 30, 40 and 50 wt%) were synthesized using solid state reaction method. X-ray diffraction analysis asserts the existence of component phases including spinel phase of CMFO and orthorhombic phase of KNN. Field emission scanning electron microscopy has been used for studying the morphology and calculation of average grain size. The temperature dependent dielectric properties including dielectric constant ( $$\varepsilon ^{\prime}$$ ) and dielectric loss (tan δ) at different frequencies has been studied and both are found to increase with incorporation of CMFO. Magnetic hysteresis loops have been measured at temperatures of 300 and 5 K. Variation of magnetization versus temperature has been studied in field cooled and zero field cooled modes. Polarization versus electric field (P–E) hysteresis loops are obtained at room temperature indicating presence of ferroelectric ordering in the composites at room temperature. The remnant polarization (2Pr) and coercive field (2Ec) are found to decrease linearly with incorporation of CMFO. ME voltage coefficient (αME) has been measured. The maximum value of αME is found to be 5.941 mV/cm-Oe for 10% CMFO–90% KNN bulk composite.

Crystal structure, dielectric, magnetic and magnetoelectric properties of xNiFe2O4-(1-x)Na0.5Bi0.5TiO3 composites

Magnetoelectric (ME) composites xNiFe2O4-(1-x)Na0.5Bi0.5TiO3 (x = 0.10,0.30,0.50) were synthesized by conventional solid state reaction method. Crystal structure and microstructural characteristics of these composites were investigated by XRD and SEM respectively. Rietveld analysis of XRD pattern confirms the coexistence of cubic (Fd3m) and rhombohedral (R3c) symmetry simultaneously in these composites. The microstructural evaluation discloses the effect of constituent phases on the average grain size of a composite. The dielectric constant (ε′) and dielectric loss (tanδ) were examined as a function of frequency within range (100 Hz to 7 MHz) and at different temperatures. The magnetic behavior of composites was determined by MH hysteresis loop which reveals their soft magnetic behavior. ME voltage coefficient was determined to study the coupling between ferrite and ferroelectric phases. The maximum value of ME coefficient α ≈ 223μV/cmOe was observed for 0.10NFO-0.90NBT sample.