Magnetoelectric Voltage Research Articles

Nonvolatile Memory and Artificial Synapse Based on the Cu/P(VDF-TrFE)/Ni Organic Memtranstor.

We demonstrate a flexible nonvolatile multilevel memory and artificial synaptic devices based on the Cu/P(VDF-TrFE)/Ni memtranstor which exhibits pronounced nonlinear magnetoelectric effects at room temperature. The states of the magnetoelectric voltage coefficient αE of the memtranstor are used to encode binary information. By applying selective electric-field pulses, the states of αE can be switched repeatedly among 2n states (n = 1, 2, 3) in a zero dc bias magnetic field. In addition, the magnetoelectric coefficient is used to act as synaptic weight, and the induced magnetoelectric voltage VME is regarded as postsynaptic potentials (excitatory or inhibitory). The artificial synaptic devices based on the Cu/P(VDF-TrFE)/Ni memtranstor display the long-term potentiation (depression) and spiking-time-dependent plasticity behaviors. The advantages of a simple structure, flexibility, multilevel, and self-biasing make the Cu/P(VDF-TrFE)/Ni organic memtranstor a promising candidate for applications in nonvolatile memory as well as artificial synaptic devices with low energy consumption.

Enhanced Magnetoelectric Coupling in BaTiO3-BiFeO3 Multilayers-An Interface Effect.

Combining various (multi-)ferroic materials into heterostructures is a promising route to enhance their inherent properties, such as the magnetoelectric coupling in BiFeO3 thin films. We have previously reported on the up-to-tenfold increase of the magnetoelectric voltage coefficient in BaTiO3-BiFeO3 multilayers relative to BiFeO3 single layers. Unraveling the origin and mechanism of this enhanced effect is a prerequisite to designing new materials for the application of magnetoelectric devices. By careful variations in the multilayer design we now present an evaluation of the influences of the BaTiO3-BiFeO3 thickness ratio, oxygen pressure during deposition, and double layer thickness. Our findings suggest an interface driven effect at the core of the magnetoelectric coupling effect in our multilayers superimposed on the inherent magnetoelectric coupling of BiFeO3 thin films, which leads to a giant coefficient of 480 Oe for a (BaTiO3-BiFeO3) superlattice with a nm double layer periodicity.

Magnetic Field Sensing Based on Magnetoelectric Coupling of Ampere Force Effect With Piezoelectric Effect in Silver/Poly(Vinylidine Fluoride)/Silver Laminated Composite

With the advantages of large piezoelectric constant, wide frequency response range and good flexibility, Poly(vinylidine fluoride) (PVDF) is receiving heightened attention as a promising alternative to traditional piezoelectric materials. This paper focuses on investigating the magnetoelectric effect of a three-layer composite consisting of a core layer of PVDF and two layers of silver-plated electrodes under the action of AC and DC magnetic fields. The resonance frequency of the measurement system is firstly determined to obtain the maximum magnetoelectric response. Then, the existence of magnetoelectric effect in the laminated sample is further verified, which is realized through the coupling of the piezoelectric effect and the Ampere forces caused by the eddy current under the DC bias magnetic field. The experimental results show that the magnetoelectric voltage has an excellent linear response to both AC and DC magnetic fields. The magnetoelectric voltage coefficient is obtained as 299.97 mV/cm·Oe at the resonance frequency under the DC magnetic field of 1000 Oe amplitude. Besides, the theoretical model of the magnetoelectric energy conversion is established, which matches well with the experimental results. Consequently, both AC and DC magnetic field sensing can be realized by observing the magnetoelectric voltage. Without requiring a magnetostrictive phase and power supply, the three-layer composite with a considerable magnetoelectric effect is promising for the application of online monitoring sensors used in the smart grid.

A Magentoelectric Coefficient Measurement System with a Free-Stress Sample Holder

With less extra stress on the testing sample, a free-stress sample holder was designed to place the sample horizontally. With the free-stress sample holder, a magnetoelectric (ME) coefficient measurement system was developed based on dynamic method. This measurement system has the hardware part and the software part, integrated by the DC magnetic field generation module, the AC magnetic field generation module, the induced ME voltage detecting module and PC software module. Then, a sample of Terfenol-D/PZT/Terfenol-D trilayer was designed and fabricated, and the relationships of its ME coefficient influenced by the DC magnetic field and the frequency of the AC magnetic field were tested using the measurement system. And the results showed that the free-stress sample holder was proven to improve the accuracy of the measurement system by less stress interference.

Giant magnetoelectric coupling observed at high frequency in NiFe2O4-BaTiO3 particulate composite.

A giant magnetoelectric voltage coupling coefficient without direct current magnetic field observed in NiFe2O4–BaTiO3 particulate composite is reported. The particulate composite was obtained by combining hydrothermal and sol–gel method, and was studied for their crystallographic structure, morphology, magnetic, dielectric and magnetoelectric properties. Results of Mössbauer spectra demonstrated the presence of interface phase in particulate composite, where the changes of the magnetic properties in composite compared to the pure NiFe2O4 also confirmed this. The particulate composite exhibits remarkable magnetoelectric effect through both static measurement and dynamic measurement. The special magnetoelectric property of the particulate composite is beneficial for applications in high frequency devices.

Self-sensing feature of the ultrasonic nano-displacement actuator in Metglas/PMN-PT/Metglas magnetoelectric composite

Self-sensing feature allows an actuator to be used as a sensor. Magnetoelectric (ME) composites consist of piezoelectric and magnetostrictive layers. ME composite is a proper candidate for the self-sensing feature in a wireless actuator due to its concurrent magnetic-charge order. In this study, the self-sensing feature of a nano-displacement ME actuator is investigated. The ME structure design, as well as the effect of geometric parameter and resonance frequency on the ME signal, is evaluated using a numerical modeling. The Metglas/PMN-PT/Metglas composite was fabricated as an ME actuator. The displacement measurement was conducted using a laser Doppler. The effect of bias field and excitation frequency on sensitivity, linearity, resolution and signal stability of actuator/sensor feature were evaluated by a magnetoelectric measurement setup. The experimental results revealed that the maximum sensitivity of actuator was achieved at the resonance frequency of about 60.7 kHz. Compared to the ME voltage, the phase angle was more reliable for application in the self-sensing feature. The actuator/sensor sensitivity was estimated at about 5.2 nm/mA and 0.64 mV/mA, respectively. Also, the output range of the sensoric feature was measured at 58–272 mV. The fatigue test revealed that the ME signal at the first resonance frequency was more stable than the second mode. The results also confirmed that the magnetoelectric signal could be promising candidate for the self-sensing feature in the ultrasonic nano-displacement actuator.

Interplay between the ferrimagnetic and ferroelectric phases on the large magnetoelectric coupling of xLi0.1Ni0.2Mn0.6Fe2.1O4–(1 − x)Bi0.8Dy0.2FeO3 composites

The multiferroic composites of ferromagnetic Li0.1Ni0.2Mn0.6Fe2.1O4 (LNMFO) and ferroelectric Bi0.8Dy0.2FeO3 (BDFO) with the general formula xLi0.1Ni0.2Mn0.6Fe2.1O4–(1 − x) Bi0.8Dy0.2FeO3 have been prepared by the solid-state reaction route. The XRD analysis has ensured that the composites are composed of a mixture of cubic spinel LNMFO and orthorhombic perovskite BDFO phases. Field Emission Scanning Electron Microscope is used to investigate the surface morphology of the studied compositions. The average grain size of the composites has reduced slightly with the enhancement of ferrite part up to 20% and after that it has increased again. The real part of the initial permeability $$(\mu^{\prime}_{i} )$$ was found to be increasing with ferrite content. The real part of dielectric constant $$(\varepsilon^{\prime})$$ exhibits dispersion at low-frequency region because of Maxwell–Wagner type interfacial polarization. The complex impedance spectroscopy has been used to separate the grain and grain boundary contribution to the total resistance. Existence of the hopping conduction mechanism has been confirmed through the study of electric modulus. The hysteresis loops of the compositions are studied to confirm the response of ferrite part to the applied magnetic field. The magnetoelectric voltage coefficients of the composites have reduced with the ferrite part. The maximum magnetoelectric voltage coefficient is nearly 158 × 103 Vm−1 T−1 for the 0.1LNMFO–0.9BDFO composite, which is about three times of the reported value compared to other composites.

Tunable Magnetoelectric Response in Cofired (Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3)/CoFe2O4 Laminated Composite

Magnetoelectric (ME) composites exhibiting strain-mediated coupling are gaining increasing interest for applications. In this paper, an enhancement of ME response on simple lead-free laminated composites (80Bi0.5Na0.5TiO3-20Bi0.5K0.5TiO3)/CoFe2O4 (BNKT/CFO) prepared by a modified cofiring processing were demonstrated, by analyzing the effect of thickness variation on ME properties. The coexistence of independent BNKT and CFO phase and the presence of a clear and well-bonded interface were confirmed. Specifically, the maximum ME voltage coefficient of laminated composite reached up to 74.59 mV/(cm·Oe) with an optimized BNKT/CFO layer thickness ratio of 1:2. The static elastic model and the equivalent circuit model were used to determine the interface coupling. Also, there is a large magnetodielectric (MD) response up to 5.1% in a magnetic field of 8 kOe. Tuning the layer thickness, the ME response of laminated composite is further optimized, which is of significance in development of magnetic-field-tuned electronic devices.

Converse Magnetoelectric Composite Resonator for Sensing Small Magnetic Fields

Magnetoelectric (ME) thin film composites consisting of sputtered piezoelectric (PE) and magnetostrictive (MS) layers enable for measurements of magnetic fields passively, i.e. an AC magnetic field directly generates an ME voltage by mechanical coupling of the MS deformation to the PE phase. In order to achieve high field sensitivities a magnetic bias field is necessary to operate at the maximum piezomagnetic coefficient of the MS phase, harnessing mechanical resonances further enhances this direct ME effect size. Despite being able to detect very small AC field amplitudes, exploiting mechanical resonances directly, implies a limitation to available signal bandwidth along with the inherent inability to detect DC or very low frequency magnetic fields. The presented work demonstrates converse ME modulation of thin film Si cantilever composites of mesoscopic dimensions (25 mm × 2.45 mm × 0.35 mm), employing piezoelectric AlN and magnetostrictive FeCoSiB films of 2 µm thickness each. A high frequency mechanical resonance at about 515 kHz leads to strong induced voltages in a surrounding pickup coil with matched self-resonance, leading to field sensitivities up to 64 kV/T. A DC limit of detection of 210 pT/Hz1/2 as well as about 70 pT/Hz1/2 at 10 Hz, without the need for a magnetic bias field, pave the way towards biomagnetic applications.

Correction to: Field-Orientation-Dependent Dynamic Strain Induced Anisotropic Magnetoelectric Responses in Bi-layered Ferrite/Piezoelectric Composites

Anisotropic magnetoelectric (ME) responses in bi-layered composites consisting of ferrites and polycrystalline/crystalline piezoelectrics were investigated by changing the applied DC magnetic field orientations, and origins for such effects were clarified by the competition between the dynamic piezomagnetic strain and the dynamic electro-mechanical strain from individual piezomagnetic/piezoelectric subsystems. Experimental results showed that maximum resonance ME voltage coefficient (MEVC) of 133.8.3 V/cm Oe under HDC = 23Oe can be obtained at θ = 0° for PMN-PT/NZFO laminate while one reached 115.3 V/cm Oe at higher field of 98Oe for θ = 75°. As rotation angle θ is varied from 0° to 360°, the HDC-orientation-dependent ME couplings were mainly determined by the dynamic piezomagnetic strain, and the dynamic piezoelectric coefficient versus θ profile can essentially track the MEVC versus θ profile. In addition, we found that the MEVC for PMN-PT/NZFO laminate is approximately twice as high as that of the PZT-8/NZFO laminate due to the stronger electro-mechanical strain of PMN-PT plates, Solid evidence was proved for the HDC-orientation-dependent ME coupling of the rectangle composite that is free of the influences of anisotropic crystalline orientation in PMN-PT plate. These findings open up a research pathway to move forward in this field and provide potential applications in vector angle sensors.

Designing ferroelectric/ferromagnetic composite with giant self-biased magnetoelectric effect

We report a simple and effective method to obtain the magnetoelectric (ME) effect at zero magnetic bias field (HDC = 0), i.e., the self-biased ME (SME) effect, using an ME laminate composite clamped at its center with its free ends loaded with magnetic tip masses. The method exploits the shifting of the magnetic hysteresis loop of the ferromagnetic (FM) layer of the laminate induced by a preapplied magnetic field (Hp) along the longitudinal direction. The optimum magnetic-field strength corresponding to the maximum of the ME voltage coefficient (αME) vs HDC curve was calculated using equations derived from correlations of magnetic coefficients. In experiments involving the laminate with an FM/ferroelectric/FM symmetrical structure, the strength of Hp was tuned to the optimum value, shifting the αME vs HDC curve along the HDC axis enough to obtain the maximum αME at HDC = 0 (αSME). To further enhance αSME, an asymmetric configuration of the laminate was designed using two different FM materials having piezomagnetic coefficients with opposite signs. The ME laminate with the asymmetrical structure exhibited a large αSME of 55.7 V cm−1 Oe−1 at its bending resonance frequency.

Magnetostriction via Magnetoelectricity: Using Magnetoelectric Response to Determine the Magnetostriction Characteristics of Composite Multiferroics

We propose a new method for determining the magnetostriction characteristics of composite multiferroics by measuring the magnetoelectric (ME) response of the material structure. It is established that the integral characteristic of the ME effect coincides to within a constant factor with the magnetostriction curve. The results of an experimental investigation of the physical properties of volume composites based on lead zirconate titanate (PZT) and nickel ferrite spinel are presented. The field dependence of the ME voltage coefficient was used to determine magnetostriction curves of composite structures containing 10–70 wt % ferrospinel.

New way the determination of magnetostrictive parameters composite multiferroics using the magnetoelectric response

The new way the determination of the thin films magnetostriction characteristics using the magnetoelectric response of composite multiferroic is supposed. The analytical expression for the magnetostriction coefficient using the field dependency of the magnetoelectric voltage coefficient is obtained. The experimental data for the bulk composite lead zirconate titanate – nickel ferrite is presented. It is shown, that the data, obtained by supposed way, are in good agreement with previous data, obtained by another way.

Field-Orientation-Dependent Dynamic Strain Induced Anisotropic Magnetoelectric Responses in Bi-layered Ferrite/Piezoelectric Composites

Anisotropic magnetoelectric (ME) responses in bi-layered composites consisting of ferrites and polycrystalline/crystalline piezoelectrics were investigated by changing the applied DC magnetic field orientations, and origins for such effects were clarified by the competition between the dynamic piezomagnetic strain and the dynamic electro-mechanical strain from individual piezomagnetic/piezoelectric subsystems. Experimental results showed that maximum resonance ME voltage coefficient (MEVC) of 133.8.3 V/cm Oe under HDC = 23Oe can be obtained at θ = 0° for PMN-PT/NZFO laminate while one reached 115.3 V/cm Oe at higher field of 98Oe for θ = 75°. As rotation angle θ is varied from 0° to 360°, the HDC-orientation-dependent ME couplings were mainly determined by the dynamic piezomagnetic strain, and the dynamic piezoelectric coefficient versus θ profile can essentially track the MEVC versus θ profile. In addition, we found that the MEVC for PMN-PT/NZFO laminate is approximately twice as high as that of the PZT-8/NZFO laminate due to the stronger electro-mechanical strain of PMN-PT plates, Solid evidence was proved for the HDC-orientation-dependent ME coupling of the rectangle composite that is free of the influences of anisotropic crystalline orientation in PMN-PT plate. These findings open up a research pathway to move forward in this field and provide potential applications in vector angle sensors.

Ferroelectricity and magnetoelectric coupling in hexagonal Lu0.5In0.5FeO3 ceramics

Recently, hexagonal rare earth ferrites (h-RFeO3) have attracted much scientific attention due to their room-temperature multiferroicity. The primary issue for h-RFeO3 is how to manipulate from nonpolar orthorhombic (Pbnm) structure to polar hexagonal (P63cm) structure, and this could be realized by the wet-chemical method, epitaxial stain engineering, or introducing chemical pressure. Another key issue for h-RFeO3 is the experimental determination of its macroferroelectricity and magnetoelectric (ME) coupling because the semiconducting nature seriously obstructs the experimental characterization. In the present work, owing to the suppressed leakage current density with decreasing temperature, saturated electrical hysteresis loops were observed in A-site substituted h-Lu0.5In0.5FeO3 ceramics at 198 K, directly demonstrating the presence of the macroferroelectricity. Room-temperature switchable ferroelectric polarization was further confirmed by the piezoresponse force microscopy. Furthermore, noticeable ME coupling with a linear ME voltage coefficient of 0.67 mV/cm Oe was observed at room temperature.

Complex magnetoelectric effect in multiferroic composites: the case of PFN-PT/(Co,Ni)Fe2O4

We report a systematic study of the magnetoelectric (ME) voltage coefficient as a complex quantity in the particulate composite of ferroelectric solid solution 0.94Pb(Fe1/2Nb1/2)O3-0.06PbTiO3(PFN-PT) with CoFe2O4(CFO) and NiFe2O4(NFO) ferrites. The results show that the real part of the ME voltage coefficient () is highly influenced by the magnetostrictive phase through . NFO produces larger at a lower magnetic field, which originates from the softer magnetic properties. In addition, was found to be positive for NFO composite, while CFO composite shows a negative ME voltage coefficient at high magnetic fields. We argue that the field dependence of can be interpreted using the dynamic piezomagnetic coefficient, . The imaginary part of the ME voltage coefficient () was also determined for all composites. Both the and show a peak at the same magnetic field, which is attributed to the maximum dynamic piezomagnetism when the magnetic domains are collectively rotated by the dc bias magnetic field. Our results show that the ME voltage coefficient in the composites of PFN-PT/(Co,Ni)Fe2O4 is highly influenced by the content, magnetic softness and field dependence behaviour of magnetostriction of the piezomagnetic phase.

Enhancement of the magnetoelectric response of polyurethane polymer / piezoceramic bi-layer materials

This paper deals with the eddy current-induced magnetoelectric (ME) effect in a bi-layered structure consisting of a piezoelectric ceramic and a thermoplastic polyurethane (PU) film with three different values of Young’s modulus. It is observed a great effect of the elastic properties of the polymer on the magnetoelectric characteristics of the laminate samples.To study the influence of the elastic modulus (c) and damping coefficient (η) of the bilayers on the DC direct current magnetic induction (Bdc) induced piezomagnetic coefficient (λ) and magnetoelectric current magnitude (I), a model based on a forced damped elastic system has been developed to calculate c, η, the first and second complex magnetoelectric coefficient αp and βp for different samples. The effect of the polymer elastic modulus on the magnetoelectric response is presented and discussed. The calculated values of the I(Bdc) and S(Bdc) obtained with this model are in good agreement with experimental data. The optimal value of the effective ME voltage coefficient (αE t) was obtained for the stiffest polyurethane grade.

Magnetic and magnetoelectric properties of Bi0.5Nd0.5FeO3 ceramics

Ceramic solid solution described by formula Bi0.5Nd0.5FeO3 was prepared by standard solid-state sintering method. X-ray diffraction proved the formation of a single-phase sample with orthorhombic structure typical of NdFeO3. Vibrating sample magnetometry revealed weak ferromagnetic behavior of the ceramics up to the Curie temperature Tc = 642 K. Local atomic configurations and local magnetic fields were investigated by 57Fe Mössbauer spectroscopy. It was shown that substitution of a single Nd3+ ion by Bi3+ ion in the orthorhombic NdFeO3 lattice causes a decrease of hyperfine magnetic field experienced by 57Fe ion by the value of 0.186 T. Measurements of the magnetoelectric effect showed that the maximal registered value of the magnetoelectric voltage coefficient was equal to 0.46 mV/(cm·Oe).

Enhanced self-bias magnetoelectric effect in locally heat-treated ME laminated composite

This study reports the improvement in the magnetoelectric (ME) coupling effect in a locally heat-treated FeBSi (Metglas)/Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 single crystal laminated composite under zero magnetic bias. The high-temperature pulse laser treatment could induce local crystallization along the laser scanning line, but adjacent domains remained still amorphous, which resulted in the thermal and lattice mismatch. Therefore, it could produce a residual stress between the crystalline and amorphous phases, which generated an internal bias field in the Metglas foil. The experimental results showed that the ME coefficient for the laser-treated laminate was enhanced to 1220 V/cm Oe at the resonance frequency of 23.32 kHz without a magnetic bias, which was two times higher than that of the untreated ME laminates. The induced ME voltage also showed a linear response to the applied AC magnetic field with an amplitude as low as 10−10 T at the resonance. The excellent ME performance could, therefore, serve as a promising and practicable application for highly sensitive magnetic field sensors under the zero bias field.

A detailed study of magnetization and magnetoelectric effect in P(VDF-TrFe) based SmFeO3 nanocomposites

In this study, we investigate magnetoelectric (ME) properties in nanocomposite films (P(VDF-TrFe))/SmFeO3 consist of ferroelectric copolymer, poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFe)) and magnetic SmFeO3 nanoparticles. Comparative magnetization vs magnetic field hysteresis loops for un-poled and electric field poled (P(VDF-TrFe))/SmFeO3 nanocomposite films demonstrate strong electric filed control of magnetization. The nanocomposite films exhibit large exchange biasing (EB) effects in magnetic measurements near spin switching temperature (~ 100 K) of SmFeO3 and the EB effects were significantly modified under electric field (E) poled conditions (at E = 200 kV/cm), indicating ME coupling. Remarkably, we observe electric field poling induced self biased converse ME effect in the (P(VDF-TrFe))/SmFeO3 nanocomposite films. The maximum magnetoelectric output voltage (α) obtained is 55 mV/cm/Oe at Hbias = 1 kOe and 25 mV/cm/Oe at Hbias = 0, after electric field poling. The discovery of self biasing phenomenon with converse ME effects at room temperature in flexible (P(VDF-TrFe))/SmFeO3 nanocomposite films is highly desirable for device applications such as electrically controlled thin memory devices and ME sensors etc.