Value Of Magnetoelectric Coefficient Research Articles

In a search for effective giant magnetoelectric coupling: Magnetically induced elastic resonance in Ni-Mn-Ga/P(VDF-TrFE) composites

Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) is a piezoelectric polymer suitable for applications in electromechanical and magnetoelectric (ME) systems. Ni-Mn-Ga alloys exhibit a giant magnetoelastic response related to their structural transformations of martensitic type, accompanied by noticeable volume changes. Together, in a thin film composite containing an ensemble of Ni-Mn-Ga particles (10 wt.%) distributed in the P(VDF-TrFE) piezopolymer, they ensure an unprecedented resonance amplification of the ME effect. Thus, a giant value of ME coefficient of 6.05 V·cm−1· Oe−1 under AC magnetic drive field of 0.2 Oe and DC bias field of 1300 Oe is experimentally observed and discussed. The physical mechanism of the proposed ME response amplification has been explained theoretically through the volume magnetostriction of the magnetostrictive particles and resonant elastic oscillation of the piezoelectric polymer matrix.

Strain mediated enhancement in magnetoelectric properties of sonochemically synthesized piezoelectric and piezomagnetic composites

Materials with magneto-electric (ME) properties are of great importance because of their demand in electronic industries. Three dimensional nano-particles of the ME-composites having the general formula (1-x)CoCr0.3Fe1.7O4(CCFO)+(x)BaTiO3(BTO) (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were obtained by comprising the piezoelectric-BTO and piezomagnetic-CCFO phases. The individual phases of CCFO and BTO were synthesized separately by ultrasonic irradiation assisted sonochemical and sol-gel routs. X-ray diffraction patterns (XRD) confirmed the well-crystalline nature of both the phases. BTO and CCFO phases were under tensile strain as confirmed by the variation in lattice constants with varying proportion of BTO and CCFO. An energy-dispersive X-ray spectroscopy spectrum confirmed the phase purity of the samples and stoichiometric concentration of elements. Magnetic properties were investigated by M − H loop measurements and dielectric properties by using RF impedance analyzer. Dielectric constant increased with the increasing percentage of BTO. The maximum value of ME coefficient (24.7 mV/cm⋅Oe) is observed for the 60%CCFO+40%BTO sample. The obtained results were discussed in the light of grain size, strain and the basic properties of the individual phases. The prepared materials can be applicable in electronic devices where high magneto-electric coefficient is desirable.

Magnetoelectric Effect in Two-Layer Composites with a Graded Magnetic Phase

Samples of a homogeneous (x = 0, 0.1, and 0.2) and multilayer ceramics with a gradient composition (x = 0.2 → 0.1 → 0 → 0.1 → 0.2) based on solid solutions of (Ni1 − xZnx)Fe2O4 nickel–zinc ferrites have been manufactured using the thick-film technology. After sintering in a two-step mode, the gradient samples exhibited a smooth non-uniform distribution of chemical elements (Zn, Ni) over the thickness. The longitudinal (αE33) and transverse (αE31) magnetoelectric effects in two-layer PZT–nickel ferrite composites have been studied. In the absence of an external magnetostatic field, the values of magnetoelectric coefficients were negligible. The maximum value of the longitudinal magnetoelectric coefficient for composites with the gradient magnetic phase was practically two times higher than value of αE33 for homogeneous structures.

Exploring magnetoelectric coupling in trilayer [Ba(Zr0.2Ti0.8)O3- 0.5(Ba0.7Ca0.3)TiO3]/ CoFe2O4/[Ba(Zr0.2Ti0.8)O3- 0.5(Ba0.7Ca0.3)TiO3] thin film

Magnetoelectric (ME) heterostructures with strong ME coupling at room temperature are of great importance due to their promising applications in next-generation devices. Here, lead-free [Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3]/CoFe2O4/[Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3] (abbreviated as (BZT-0.5BCT)/CFO/(BZT-0.5BCT)) trilayer thin film has been deposited on Pt/Ti/SiO2/Si (100) substrate by pulsed laser deposition technique. Dielectric properties of trilayer thin film show the relaxor behavior and high value of dielectric constant (∼2.2 × 103) with low dielectric loss (∼0.16) at frequency 100 Hz at room temperature. Typical ferroelectric and magnetic hysteresis loops were found with large electric polarizations (Ps = 12.14 μC/cm2, Pr = 6.0 μC/cm2) and magnetization (Ms = 246 emu/cc and Mr = 66.6 emu/cc), respectively. The change in PE loop on the application of magnetic field represents the strong ME coupling. The high value of ME coefficient (αME∼0.74 V/cm.Oe) was detected at room temperature which indicates its potential application for multifunctional ME devices.

Relaxor (Pb0.7Bi0.3)(Mg0.231Nb0.462Fe0.3)O3 electronic compound for magnetoelectric field sensor applications

A solid solution between relaxor ferroelectric PbMg1/3Nb2/3O3 (PMN) and multiferroic BiFeO3 (BFO) has been synthesized by a solid-state chemical reaction route. The comprehensive x-ray diffraction studies of (1 − x)PbMg1/3Nb2/3O3–xBiFeO3 [(1 − x)PMN–xBFO] confirm the realization of stable and orthorhombic crystal systems. From the dielectric study, relaxor behavior has been observed, which is corroborated by a broadened peak and diffusive phase transition. The magnetoelectric (ME) properties have been explored through P–E loop, M–H loop, and magnetoelectric coefficient analyses. The simultaneous occurrence of polarization and magnetization reveals the ME coupling response of the PMN–BFO compounds. Excellent values of PS = 15.94 μc/cm2, Pr = 7.68 μc/cm2, MS = 12.96 emu/g, Mr = 1.25 emu/g, and ME coefficient value of 220 mV/cm Oe for x = 0.3 are obtained, which is helpful for magnetoelectric field sensor applications. To ascertain its sensing capability, a prototype has been developed, and the sensing behavior of the device has been established by placing it near a designed helical coil electromagnetic field generator structure.

Structural, dielectric and magnetoelectric coupling analysis in SrBi2Nb2O9–CoFe2O4 composites

Ferroelectric–magnetic composites of SrBi2Nb2O9–CoFe2O4 (SBN–CFO) were synthesized via conventional solid state reaction route. The powder X-ray diffraction, Raman spectroscopy and scanning electron microscopy measurements confirm the existence of two chemically separated phases and phase purity in the SBN–CFO composites. Magnetization measurements confirm the enhanced values of the magnetic parameters. The change in the area of the ferroelectric P vs. E loops with frequency confirms the enhanced ferroelectric nature of the SBN–CFO composites. The quantified maximum values of magnetoelectric coefficient (α) are observed from the P vs. E loop measurements in the influence of applied magnetic field and found to be 4.475 mV cm−1 Oe−1 at 688 Oe for SBN–0.1CFO and 3.389 mV cm−1 Oe−1 at 1000 Oe for SBN–0.2CFO composites, respectively. The shifting in the peaks of temperature-dependent dielectric maxima towards the higher temperature side confirms the relaxor behaviour in the SBN–CFO composite samples.

La2NiMnO6/poly(vinylidene fluoride) nanocomposites with enhanced magnetoelectric voltage

Multiferroic polymer composites of La2NiMnO6 and poly(vinylidene fluoride) (PVDF) in the form of disks and thick films were made via a two-step method and a solution casting method, respectively. These composite samples are studied via powder x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). The XRD data revealed the biphasic (P21/n + R-3c) crystal symmetry of La2NiMnO6 nanoparticles in the disk samples but monophasic (R-3c) crystal symmetry in the film sample. The formation of an electroactive β-phase of PVDF is observed in the FTIR spectra of a composite film sample. Estimation (via FTIR data) revealed the maximum β-phase fraction of PVDF (∼37%) and zero porosity (in FESEM images) for the film sample. The magnetoelectric (ME) voltage measurement on these composite samples show significant ME voltage for temperatures as high as 400 K, which otherwise is zero for T > 277 K in La2NiMnO6. Among the three composites, the film sample exhibited the maximum value of a first-order ME coefficient of 9.6 mV/cm Oe, and this value is at least two orders higher than that of the La2NiMnO6 pellet. Such a high value of ME coefficient favors this sample for its utilization in device applications and thus makes it technologically viable for ME based applications.

Effect of Addition of NZF Nanoparticles on Ferroelectric, Magnetic and Magnetoelectric Properties of BST-NZF Composite

In this work, multiferroic composite has been prepared using nickel zinc ferrite as ferromagnetic phase and barium strontium titanate as ferroelectric phase. Composite samples were characterized for ferroelectric, piezoelectric, magnetic and magnetoelectric properties. Piezoelectric and ferroelectric properties of the composite samples get deteriorated, while magnetic properties get improved, with increase in content of NZF nanoparticles. Composite sample containing 30 wt.% of NZF nanoparticles possesses the highest value of magnetoelectric coefficient.

Size-Dependent and Multi-Field Coupling Behavior of Layered Multiferroic Nanocomposites.

The prediction of magnetoelectric (ME) coupling in nano-scaled multiferroic composites is significant for nano-devices. In this paper, we propose a nonlinear multi-field coupling model for ME effect in layered multiferroic nanocomposites based on the surface stress model, strain gradient theory and nonlinear magneto-elastic-thermal coupling constitutive relation. With this novel model, the influence of external fields on strain gradient and flexoelectricity is discussed for the first time. Meanwhile, a comprehensive investigation on the influence of size-dependent parameters and multi-field conditions on ME performance is made. The numerical results show that ME coupling is remarkably size-dependent as the thickness of the composites reduces to nanoscale. Especially, the ME coefficient is enhanced by either surface effect or flexoelectricity. The strain gradient in composites at the nano-scale is significant and influenced by the external stimuli at different levels via the change in materials’ properties. More importantly, due to the nonlinear multi-field coupling behavior of ferromagnetic materials, appropriate compressive stress and temperature may improve the value of ME coefficient and reduce the required magnetic field. This paper provides a theoretical basis to analyze and evaluate multi-field coupling characteristics of nanostructure-based ME devices.

Lead free xNiFe2O4 – (1-x)ErMnO3 (x = 0.1, 0.3 and 0.5) multiferroic nanocomposites: Studies of magnetoelectric coupling, AC electrical and magnetodielectric properties

Magnetoelectric coupling in xNiFe2O4 (NFO) – (1-x) ErMnO3 (EMO) (x = 0.1, 0.3 and 0.5) lead free multiferroic nanocomposites prepared through pyrophoric reaction method has been investigated at room temperature. The value of magnetoelectric coefficient is found to ∼1.48 mV/cmOe at a frequency of 1 kHz in longitudinal configuration for 0.5NFO – 0.5EMO nanocomposites. The observed magnetoelectric coefficient for all those nanocomposites may be due to the presence of magnetostriction and magnetodielectric properties of piezomagnetic component of the composites. Also, the value of magnetoelectric coefficient is found to depend on ErMnO3 volume fraction. Moreover, magnetic field tuning of ac electrical properties have been observed. Nyquist plots at different applied dc magnetic field show the significant contributions of grain boundaries and grain of the samples. The magnetodielectric constant is found to be ∼47% at a frequency of 1 kHz for 0.5NFO – 0.5EMO nanocomposites.

Magnetic field induced polarization and magnetoelectric effect in Na0.5Bi0.5TiO3–Co0.75Zn0.25Cr0.2Fe1.8O4 multiferroic composite

Abstract Multiferroic composites of Zn-Cr substituted cobalt ferrite (Co0.75Zn0.25Cr0.2Fe1.8O4) (CZCFO) nanoparticles and lead-free piezoelectric sodium bismuth titanate Na0.5Bi0.5TiO3 (NBT) having composition (1 − x) Na0.5Bi0.5TiO3 + (x)Co0.75Zn0.25Cr0.2Fe1.8O4 (x = 0.0, 0.25, 0.5, 0.75, 1.0) were investigated in this study. Ferromagnetic-CZCFO and ferroelectric-NBT phases were synthesized via sol-gel auto combustion route and solid-state reaction methods respectively. The structural properties of composite materials were studied using X-ray diffraction (XRD) technique. Intense and sharp peaks observed in XRD patterns confirm that both the phases are well crystalline in nature. Two separate phases of CZCFO and NBT are present in composite material without any impurity or chemical reaction among them. The morphology of prepared samples was studied via scanning electron microscopy confirming that composite materials are well-densified and homogenous grain size distribution. The magnetic hysteresis loops of multiferroic composite were investigated by using vibrating sample magnetometer at room temperature. The lead free multiferroic composite exhibiting a large converse magneto-electric (ME) effect at room temperature. The maximum value of ME coefficient (αME = 7.92 kV/cm) is obtained at x = 0.50. Furthermore, electrical properties of nanocomposite material were studied by P-E hysteresis loop and dielectric measurements at room temperature.

A nonlinear magneto-mechanical-thermal-electric coupling model of Terfenol-D/PZT/Terfenol-D and Ni/PZT/Ni laminates

A nonlinear magneto-mechanical-thermo-electric coupling finite element model is established for the Terfenol-D/PZT and Ni/PZT laminates structure respectively, based on Maxwell electromagnetic equations and nonlinear constitutive equations of giant magnetostrictive materials. The magnetoelectric (ME) coefficients of the two laminates with considering the coupling stress or without considering the coupling stress are calculated respectively. The results indicate that the predicted values of ME coefficient of our model are very well in agreement with the experimental datas both in the low, intermediate and high magnetic field for the two kinds of materials structures at different temperatures (most of previous theoretical models just give the well comparison in low and intermediate field). The coupling stress has a significant effect on the ME coefficient for the Terfenol-D/PZT laminate, but little effect for the Ni/PZT laminate. The ME coefficient with considering coupling stress is smaller than that without considering coupling stress. Besides, the magnetic flux density, displacement and voltage distribution characteristics of ME laminates at different temperatures and pre-stresses are also detailed investigated. It has been shown a noteworthy phenomenon that the sensitivity of ME effect on temperature and/or pre-stress can be tuned by the pre-stress and/or temperature, respectively. Adjusting pre-stress can reduce the sensitivity of ME effect on temperature, which may promote the stability of ME devices operating in complex environments.

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.

Multiple broadband magnetoelectric response in Terfenol-D/PZT structure**Project supported by the National Natural Science Foundation of China (Grant Nos. 11702120, 11372120, 11421062, and 11572143) and the Fundamental Research Funds for the Central Universities, China (Grant No. lzujbky-2016-106).

In this paper, a novel magnetoelectric (ME) composite structure is proposed, and the ME response in the structure is measured at the bias magnetic field up to 2000 Oe (1 Oe = 79.5775 A·m−1) and the excitation frequency of alternating magnetic field ranging from 1 kHz to 200 kHz. The ME voltage of each PZT layer is detected. According to the measurement results, the phase differences are observed among three channels and the multi-peak phenomenon appears in each channel. Meanwhile, the results show that the ME structure can stay a relatively high ME response within a wide bandwidth. Besides, the hysteretic loops of three PZT layers are observed. When the frequency of alternating current (AC) magnetic field changes, the maximum value of ME coefficient appears in different layers due to the multiple vibration modes of the structure. Moreover, a finite element analysis is performed to evaluate the resonant frequency of the structure, and the theoretical calculating results accord well with the experimental results. The experiment results suggest that the proposed structure may be a good candidate for designing broadband magnetic field sensors.

A flexible multiferroic composite with high self-biased magnetoelectric coupling

Polymer-matrix multiferroic composites with self-biased magnetoelectric (ME) coupling hold promises in flexible energy harvester, magnetic field sensors and actuators, etc. Using CoFe2O4 (CFO) nanoparticles and multi-walled carbon nanotubes (CNTs) as fillers to the polyvinylidene fluoride (PVDF) matrix, piezomagnetic films (CFO-CNT-PVDF, also named as M layers) with different volume fractions of CFO and a fixed percentage of CNTs are obtained, which also serve as the electrode. By employing the layer of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE), named as P layer) sandwiched between the two conductive layers of CFO-CNT-PVDF, and followed by hot-pressing, three-layered multiferroic composite CFO-CNT-PVDF/P(VDF-TrFE)/CFO-CNT-PVDF (named as M/P/M) are prepared. The ME coupling increases with the volume fraction of CFO nanoparticles. The maximum self-biased and peak values of ME coefficient (αME) reach 16.7 mV cm−1 Oe−1 and 25.8 mV cm−1 Oe−1, respectively. Measurements on the relationship between the magnetostriction and static magnetic field (Hs) are performed for the CFO-CNT-PVDF films with different volume fraction of CFO. Based on the equivalent circuit model, the self-biased and peak values of αME are calculated for the ME composites, which fit well with the experimental data. The results imply that it is the high piezomagnetic coefficient, as well as the remnant magnetization of the M layer, contributes to the observed strong self-biased ME coupling for the CFO-CNT-PVDF/P(VDF-TrFE)/CFO-CNT-PVDF composite. Since the mechanical flexibility is also of great importance regarding the practical device applications, the stress-strain behavior for the CFO-CNT-PVDF layers is studied. With the volume fraction of CFO increases, both fracture strength (σf) and fracture strain (εf) decrease. The results offer a guideline for selecting proper ME composites on specified device applications.

Room temperature magnetoelectric coupling of 0.4Zn0.3Ni0.7Fe2O4- 0.6PbZr0.52Ti0.48O3 multiferroic nanocomposite

We have investigated room temperature magnetoelectric coupling of 0.4Zn0.3Ni0.7Fe2O4 - 0.6PbZr0.52Ti0.48O3 multiferroic nanocomposite prepared through low temperature pyrophoric chemical process and solid state route. Multiferroic magnetoelectric (ME) composite have gained lots of interest from past few years due to its potential applications in magnetic field sensors device applications. The structural characterization has been carried out through x- ray diffraction technique, which reveals simultaneous existence of both the phases of nanomatric grains. The value of magnetoelectric coefficient in transverse and longitudinal configurations is found to ∼ 3.7 and ∼ 3.2 mV/cmOe, respectively. The observed magnetoelectric effect is may be due to magnetostriction of the sample.

Relationship between the ferromagnetic phase and the magnetoelectric coupling in hot pressed Pb(Mg1/3Nb2/3)O3-PbTiO3 based particulate composites

ABSTRACTThe influence of ferromagnetic phase properties on the magnetoelectric response of hot pressed particulate composites formed by 80 mol% of 0.675[Pb(Mg1/3Nb2/3)O3]–0.325[PbTiO3] as piezoelectric matrix and 20 mol% of NiFe2O4, CoFe2O4 or BaFe12O19 phases was analyzed. The hot pressing sintering method was suitable for obtaining composites with apparent density higher than 94% and electric resistivity close to 109 Ω.m, independently of the ferromagnetic phases used. The magnitude of the magnetoelectric coupling seems to be governed by the piezoelectric properties of ferroelectric PMN-PT matrix, and the zero bias magnetoelectric coefficient values are determined by the ferromagnetic hardness of the magnetic phase.

Y3Fe5O12/Na,Bi,Sr-doped PZT particulate magnetoelectric composites

Magnetoelectric (ME) composites of Na, Bi, Sr substituted lead zirconate titanate (PZT) and yttrium iron garnet having representative formula (100−х)wt% Na,Bi,Sr-doped PZT (PZTNB-1)+хwt% Y3Fe5O12 (YIG) with х=10–90 were manufactured using powdered components obtained through sol–gel processes. It is shown that the decrease in sintering temperature provided by the use of finely dispersed PZTNB-1 and YIG powders allows to significantly reduce content of fluorite-like foreign phase based on zirconium oxide, which forms due to the interfacial interaction during heat treatment and becomes stabilized by yttrium oxide. Connectivity has considerable effect on the value of ME coefficient of composite ceramics. With the same x value, ΔЕ/ΔН characteristic decreases when changing from 0–3-type structured composites (PZT grains embedded in ferrite matrix) to 3-3-(interpenetrating network of two phases) and especially 3-0-type samples (YIG grains embedded in PZT matrix); in the last case this can be attributed to the substrate clamping effect when ferrite grains are clamped with piezoelectric matrix. ΔЕ/ΔН value of 0–3 composites with х=40–60wt% was found to be ∼1.6mV/(cmOe).

Weak ferromagnetism and magnetoelectric effect in multiferroic xBa0.95Sr0.05TiO3–(1−x)BiFe0.9Gd0.1O3 relaxors

Multiferroic xBa0.95Sr0.05TiO3–(1−x)BiFe0.9Gd0.1O3 [xBST–(1−x)BFGO], where x=0.00−0.40, have been synthesized by the conventional solid-state reaction method. The crystalline phase, microstructure, relaxor behavior, ac conductivity, impedance spectroscopy, dc magnetic properties, complex initial permeability and magnetoelectric coefficient of these solid solutions have been investigated. The crystal structure is found to change from rhombohedral in BFGO rich compositions to cubic when x≥0.30. Room temperature dielectric properties are investigated within the frequency range from 1kHz to 1MHz and found to increase with BST content. The frequency dependence of high temperature dielectric measurements indicated that the composites with x≥0.20, exhibit relaxor ferroelectric behavior. The ac conductivity obeys the Jonscher’s universal power law and BST helps to enhance the electrical conductivity of the composites. Studies of impedance spectroscopy suggest that only grains have the contribution to the conductivity mechanism in this material. Magnetizations as a function of applied magnetic field measurements show weak ferromagnetism for 0.10≤x≤0.30 composites. The maximum value of remnant magnetization is found to be 0.565×103A/m (=0.08emu/g) for x=0.25 which is better than previously reported BaTiO3–BiFeO3 systems. The complex initial permeability is found to improve with the increase in BST concentration due to the reduction of oxygen vacancies. In addition, an enhanced magnetoelectric (ME) coupling is also observed and determined by the ME coefficient. The maximum value of ME coefficient is found to be 21.71×10−4V/A (=1.67mV/cmOe) for the x=0.25 composition. The BST–BFGO solid solutions show high-performance multiferroic properties and can be selected for further investigation.

Length dependence of the resonant magnetoelectric effect in Ni/Pb(Zr,Ti)O3/Ni long cylindrical composites

Magnetoelectric (ME) effect was studied in the long cylindrical Ni/Pb(Zr,Ti)O3/Ni layered composites prepared by electroless deposition. Three significant resonant peaks have been observed in the dependence of the ME voltage coefficient on the magnetic field frequency. The height of the composite cylinder has an important impact on the ME effect. With the height of the cylinder increase, the value of ME coefficient at static or low-frequency case increases, while the resonant frequencies decrease. Furthermore, the ME effect at the individual resonant frequencies can be weakened or enhanced due to the coupling of radial and axial vibration modes. The experimental values of resonant frequencies are in good agreement with the calculated ones. The results are useful for magnetoelectric devices with controllable multifrequency operation.