ME Voltage Coefficient Research Articles

Modeling the Magnetoelectric Composites in a Wide Frequency Range.

This article presents a general theory of the ME effect in composites in the low- and high-frequency ranges. Besides the quasi-static region, the area of electromechanical resonance, including longitudinal, bending, longitudinal shear, and torsional modes, is considered in more detail. To demonstrate the theory, expressions of ME voltage coefficients are obtained for symmetric and asymmetric layered structures. A comparison is made with the experimental results for the GaAs/Metglas and LiNbO3/Metglas structures. The main microwave ME effect, consisting of the FMR line shift in an electric field, for the ferromagnetic metals, their alloys, and YIG ferrite using various piezoelectrics is discussed. In addition to analytical calculations, in the article, finite element modeling is considered. The calculation methods and experimental results are compared for some composites.

Magnetoelectric Properties of Ni-PZT-Ni Heterostructures Obtained by Electrochemical Deposition of Nickel in an External Magnetic Field

This paper studied the influence of external electric and magnetic fields on the magnetoelectric properties of layered structures of metal-piezoelectric-metal. The structures under study had the shape of a square 4 mm wide and were obtained in two steps: first, by the chemical deposition of nickel with a thickness of 0.5 μm, and then by the electrochemical deposition of nickel with a thickness of 50 μm on each side onto a lead zirconate–lead titanate substrate. Electrochemical deposition was carried out without a magnetic field on both non-polarized and polarized ceramics. Electrochemical deposition was also carried out in a magnetic field on a non-polarized and polarized PZT ceramic substrate. A magnetic field of 500 Oe at electrochemical deposition was applied in all cases in the direction of structure polarization. The maximum ME voltage coefficient 300 mV/(cmOe) was obtained at transverse orientation at bias magnetic field near 20 Oe.

Исследование магнитоэлектрических продольно-сдвиговой и крутильной мод в несимметричных структурах

The theoretical study of possibility for the torsional mode identification against the background of longitudinal-shear one in asymmetric ME composites Metglas / GaAs and Metglas / bimorph LN Zyl + 45° is carried out in this paper. It is determined that ME composites with bimorph LN Zyl + 45° are better to use as a piezoelectric to study the torsional mode of the ME effect. This is due to the fact that the longitudinal-shear mode is not excited in the ME composite with a bimorph LN Zyl + 45°, and the ME voltage coefficient depends only on the torsional mode.

Enhanced non-bias-field magnetoelectric response with high detectivity in a sensing system based on electret film and magnetostrictive material

An electret film and a magnetostrictive rod were used to combine a magnetoelectric sensing system. The dynamic magnetoelectric measurement was used to investigate the voltage output of the combined system. A significant non-bias-field magnetoelectric response was observed. The capacitance and magnetoelectric voltage coefficient were significantly affected by the AC and DC magnetic field. The ME voltage coefficient exhibited a step decrease with an increase in the DC field. The maximum tunability of the magnetoelectric voltage coefficient was 99.8%. The limit of detection of the AC magnetic field decreased rapidly with a very high value at lower frequencies and decreased slowly with a very low value at higher frequencies. The minimum value of the limit of detection was approximately 0.016 Oe. These findings indicated the combination for potential applications in magnetic detectors, magnetoelectric sensors, switches, and energy converters.

Enhanced performance of magnetoelectric voltage coefficient in giant magnetostrictive (Ni0.7Mg0.3Fe2O4)/piezoelectric (BaZr0.2Ti0.8O3) composites

The non-toxic lead-free multiferroic composite samples Ni0.7Mg0.3Fe2O4/BaZr0.2Ti0.8O3 were synthesized by using standard double sintering ceramic method. The composite samples are found to exhibit dielectric response, which might be associated with Maxwell-Wagner type interfacial polarization and Koop's phenomenological theory. The variation of DC conductivity with respect to temperature revealed the conduction of electrons i.e. due to the small polarons hopping mechanism. The synthesized ME composite samples show a representative magnetic hysteresis (M − H) loop type behaviour at room temperature. In a previous report, the response of ME voltage coefficient 4.262 mVcm-1.Oe was determined for (30%) Ni0.8Mg0.2Fe2O4 + (70%) BaZr0.2Ti0.8O3 composites at 5.0 kOe applied DC magnetic field. But in this report, we improved the ME voltage coefficient for the composition 50% (Ni0.7Mg0.3Fe2O4) + 50% (BaZr0.2Ti0.8O3) which is a lead-free ME composite with the massive ME voltage coefficient of 8.562 mV/cm.Oe was achieved. Hence, the estimated results can provide experimental guidance for the optimal design of high-performance magnetoelectric devices and render better support for the technological development in the field of magnetoelectricity.

Mathematical modelling of magnetoelectric effect in multiferroic in thickness-shear mode region

The article discusses the magnetoelectric effect in the thickness-shear mode region in a layered structure of a piezoelectric bimorph and a magnetostrictive material. Numerical estimates according to the proposed theoretical model of the magnetoelectric effect in the structure of the langatate bimorph and yttrium-iron garnet show that the value of ME voltage coefficient is much higher than for the bilayer of langatate and yttrium-iron garnet.

Undistorted 180° phase reversal of magnetoelectric coupling in bi-layered multiferroic laminate

A methodology of rotating the applied static magnetic field on Ni0.8Zn0.2Fe2O4 (NZFO)/PZT-8 magnetoelectric laminate, was introduced to realize 180° phase reversal with constant amplitude, which is invariably required for phase-based communication system, engineering technology and microelectronic devices. Through further decoding the phase information existed in magnetoelectric coefficient, we found that the undistorted 180° phase reversal can be achieved once the applied field was reversed. Moreover, piezomagnetic response can essentially track the magnetoelectric response under optimum bias with the variations of rotation angle, and then the origins can be well explained. Experimental results show that the maximum resonance ME voltage coefficient of +51.72 V/cm Oe and −51.93 V/cm Oe were obtained in angle of θ = 0° and 180°, respectively. These results provide great possibilities for practical applications in ME phase shifters and inverters.

Influence of clamping effect in BaTiO3 film on the magnetoelectric behavior of layered multiferroic heterostructures

The experimental observation and analysis for the influence of clamping effect on the magnetoelectric properties of the bilayer La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) and trilayer LSMO/BTO/LSMO heterostructures were reported. Because the significant two-dimensional clamping effect caused by the lattice mismatch of the constituting layers, the relative dielectric constant and the ferroelectric coercive field of the trilayer heterostructure was lower than that of the bilayer one. Furthermore, the variation in ME voltage coefficient (αE) as a function of frequency for the two heterostructures was found to exhibit a monotonous increasing tendency. The value of αE for the trilayer heterostructure was little lower than that of the bilayer one, that is because the clamping effect suppressed both the ferroelectric properties of BTO and the transferred strain at the hetero interface.

Magnetopiezofiber

The results of the magnetoelectric effect study in the magnetopiezofiber are presented. Magnetopiezofiber consists of mechanically coupled piezoelectric (one layer of lead zirconate titanate) and magnetostrictive (two metglass layers) fibers. The layers were joined together by epoxy under pressure and heating. The sample active area dimensions were 28x7x0,34 mm. The study of the magnetoelectric effect was carried out in the frequency range from 0 to 150 kHz and external magnetic field range from 0 to 100 Oe. Maximum value of the ME voltage coefficient αE = 62,75 V/cm-Oe was measured on the electromechanical resonance frequency f = 61 kHz with an external magnetic field of 4,5 Oe. Obtained results indicate the prospects of the proposed design in magnetoelectric devices application.

All-printed multilayer materials with improved magnetoelectric response

For the first time is reported the development of a screen printed flexible magnetoelectric material based on P(VDF–TrFE), PVDF and CoFe2O4. The ME voltage coefficient of 164 mV cm−1Oe−1at a longitudinal resonance frequency of 16.2 kHz, the highest reported in the literature, certifies the use of the printed material on printed electronics, sensors, actuators, and energy harvesters.

Influence of Sm and Nb on the structural, electric, magnetic and magneto-electric properties of BaTiO3-Li0.5Fe2.5O4 composite ceramics grown by the conventional solid state technique

The Sm and Nb doped BaTiO3-Li0.5Fe2.5O4 composite ceramics having chemical formulae (90)BaTi(1−2x)NbxSmxO3 + (10) Li0.5Fe2.5O4 (x = 0, 0.05 and 0.1) were synthesized using conventional solid state technique. The structural, morphological, magnetic, dielectric, ferroelectric and magneto-electric properties of composites have been studied. The XRD measurement reveals the absence of peaks pertaining to impurities and strongly confirms the high crystalline nature of all the composites. From FESEM images, the average grain size of composites increases with increase in the concentration of Nb and Sm. The VSM studies confirm the soft magnetic nature of all the composites. The dielectric measurements confirm the increase in the transition temperature (Tc) of the BTL composite with an increase in the concentration of Nb and Sm. The P–E studies confirm that the ferroelectric nature of the BTL composite softens after doping Nb and Sm in it. The ME voltage coefficient value confirms the uniform growth of grains in all the composites and reveals a strong interaction between ferroelectric and magnetic orders.

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.

Dielectric, magnetic and magnetoelectric studies of lithium ferrite synthesized by solid state technique for wave propagation applications

Abstract The electric and magnetic properties of a lithium ferrite (LF) synthesized using the solid state reaction technique have been reported. The XRD studies reveal the cubic nature, from which the crystallite size and the lattice constant are determined to be 16.84 nm and 2.847 A repectively. The FESEM confirms the coarseness in the samples with a low porosity. Variations of the dielectric constant and dielectric loss with temperature at different frequencies have been studied. The dielectric constant increases more steeply in the negative direction with increasing temperature beyond 500 °C at 100 kHz. The impedance plot exhibits almost complete semicircles at all temperatures, whose centers situated on the real axis. This suggests that the sample obeys the Debye behavior. The magnetic studies reveal a soft magnetic characteristic of LF. The ME voltage coefficient decreases with increasing magnetic field and attains a constant value in the high magnetic field.

Magnetoelectric behaviors in BaTiO3/CoFe2O4/BaTiO3 laminated ceramic composites prepared by spark plasma sintering

The BaTiO3 (BTO) / CoFe2O4 (CFO) / BaTiO3 (BTO) laminated ceramic composites were prepared via spark plasma sintering (SPS). The ceramic composites were highly dense with clear boundaries between the three layers. The short time and low temperature required for densification during the SPS process diminish the possibility for unwanted reactions to occur. The BTO/CFO/BTO laminated ceramic composites exhibit excellent ME properties including: (1) maximal ME voltage coefficient as high as ~ 1.0 V/Oe cm; (2) obvious AC magnetic field frequency response and sensitivity from 102 to 107 Hz; (3) perfect ME anisotropy matches well with the theoretical fitting curve; (4) giant transverse ME voltage coefficient as large as ~ 4.1 V/Oe cm at resonance frequency of ~ 105 Hz. It is possible to fabricate several kinds of ME function devices with the BTO/CFO/BTO laminated ceramics prepared in this work.

Magnetic effects on polarization response in particulate magnetoelectric Bi0.5Na0.5TiO3-La0.67Sr0.33MnO3 composites

Biphase particulate magnetoelectric ceramics (1-x)Bi0.5Na0.5TiO3-xLa0.67Sr0.33MnO3 (x = 0.05, 0.15, 0.25 and 0.35) were prepared using the powder-in-sol precursor hybrid method. Effect of magnetic field on polarization response in composites was studied, by analyzing the magnetodielectric effect and ferroelectric loops under the applied magnetic field. The switching of magnetodielectric effect and the variation ferroelectric polarization is mainly determined by the competitive mechanisms of magnetoresistance and magnetostriction. Furthermore, the direct magnetoelectric output was carried out and the maximum ME voltage coefficient reached up to 19.1 mV/cm·Oe for the x = 0.15 composite.

Large resonance magnetoelectric response in Ni(Terfenol-d)/Pb(Zr,Ti)O3 bilayer laminate composites

In this work we report magnetoelectric laminate composites made up of negative magnetostrictive Ni plates, positive magnetostrictive Tb0.3Dy0.7Fe2 (Terfenol-d) plates and piezoelectric Pb(Zr,Ti)O3 (PZT) plates, in which negative and positive magnetostrictive plates are bonded on the piezoelectric plate and conjugate longitudinally with various orders. Both Ni-Terfenol-d-Ni/PZT and Terfenol-d-Ni-Terfenol-d/PZT composites are constructed and compared with Ni/PZT and Terfenol-d/PZT composites. The bias magnetic field and the frequency dependences of the magnetoelectric coefficient suggest that Ni-Terfenol-d-Ni/PZT is an optimal configuration with excellent magnetoelectric effects such as a large magnetoelectric coefficient at a low bias magnetic field and a low resonance frequency at which the maximum ME voltage coefficient appears. Besides, compared with most of other bulk composites configuration with Terfenol-d plates, the Ni-Terfenol-d-Ni/PZT composite reduces the Terfenol-d usage. We believe that the Ni-Terfenol-d-Ni/PZT composite is useful for the application due to its simple configuration and large resonance magnetoelectric response at a low frequency.

Correlation between magnetoelectric coupling effect and dielectric properties of La0.7Sr0.3MnO3/BaTiO3 bilayer heterostructure

By using pulsed laser deposition, the epitaxial La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) bilayer heterostructures were grown onto various substrates. The variation in ME voltage coefficient (αE) as a function of frequency was found to exhibit a monotonous increasing tendency. In the low frequency range, the value of αE increased sharply, while it increased slightly in high frequency range. Furthermore, the value of relative dielectric constant (εr) for BTO layer was found to decrease rapidly at first, and then it slowly increased in high frequency range. It was experimentally proved a well-known relation between the ME coupling and dielectric properties, which shown that the frequency dependence of ME voltage coefficient could be calculated and predicted by the dielectric constant curves of corresponding ferroelectric layer.

Significant enhancement of resonance magnetoelectric coupling in miniaturized lead-free NiFe2O4–BaTiO3 multilayers

With increasing demands toward device miniaturization, Pb-free magnetoelectric laminates (MELs) with a small lateral dimension of ∼3 × 3 mm2 have been synthesized by the tape-casting method. The MELs are composed of alternating layers of magnetostrictive NiFe2O4 and piezoelectric BaTiO3 with a uniform single layer thickness of t = 50 and 15 μm, respectively. Both laminates exhibit much larger longitudinal ME voltage coefficient αE33 than the transverse ME voltage coefficient αE31 at both off-resonant and resonant frequencies, which is attributed to the preferential easy-plane alignment of the magnetic moments. Furthermore, enhancement in αE33 by more than 5 times has been achieved upon decreasing t from 50 to 15 μm in both resonance and off-resonance conditions. The enhanced αE33 values indicate that nearly ideal interface coupling between the ferromagnetic and piezoelectric layers is realized in the miniaturized, thinner MEL, pointing to practical application potential towards developing mass-produced, low-cost ME devices.

Study of electric, magnetic properties and improvements in ME effects of NMFO + BZT particulate composites

ME composite materials with the general formula (x)Ni0.9Mg0.1Fe2O4+(1−x)BaZr0.2Ti0.8O3 (x=0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized by solid state reaction method. X-ray diffraction (XRD) study reveals the coexistence of piezomagnetic and piezoelectric phases without interacting with each other. The cubic spinel structure of Ni0.9Mg0.1Fe2O4 (NMFO) piezomagnetic phase and tetragonal perovskite structure of BaZr0.2Ti0.8O3 (BZT) piezoelectric phase for synthesized composites were confirmed by XRD measurements. The lattice constant of piezomagnetic and piezoelectric phases increases with increase in composition of the substituent. The dielectric constant and dielectric loss tangent of the composites measured as a function of frequency in the range 10Hz–1MHz at room temperature are found to decrease rapidly in low frequency regime and remain constant in high frequency regime shows the dielectric dispersion behavior. The magnetic properties of the composites have been studied using M-H hysteresis loops to see the response of the magnetic field on the NMFO phase in the composites. The saturation magnetization increases with increase in the mole% of piezomagnetic phase in the composites. The ME voltage coefficient measured as a function of the applied DC magnetic field; shows maximum value (8.622mVcm−1Oe) for (50%)NMFO+(50%)BZT bulk composites. The addition of NMFO and BZT enhances the ME properties of the composites.

Growth and magnetoelectric properties of (00l)-oriented La0.67Sr0.33MnO3/PbZr0.52Ti0.48O3 heterostructure films

C-axis oriented La0.67Sr0.33MnO3(LSMO)/PbZr0.52Ti0.48O3(PZT) films are fabricated successfully by sol-gel method on LaAlO3 (00l) substrates. The structure, composition and morphology of the films are investigated by X-ray diffractometer (XRD, θ-2θ scan, ω-scan and ϕ-scan), X-ray photoelectron spectroscope (XPS), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). The electric and magnetic properties of randomly and c-axis oriented LSMO/PZT films are studied comparably using ferroelectric testing apparatus and physical property measurement system (PPMS). It is found that the epitaxial LSMO/PZT composite films show well controlled growth along c-axis, and much better magnetoelectric properties than the randomly oriented ones. The ME voltage coefficient increases from 23mVcm−1Oe−1 for the randomly oriented LSMO/PZT composite films to 52mVcm−1Oe−1 for c-axis oriented ones prepared using the low cost sol-gel method presented in this study, which shows high potential in promising applications.