Giant Magnetoelectric Effect Research Articles

Control of the Magnetism and Magnetic Anisotropy of a Single-Molecule Magnet with an Electric Field

Through systematic density functional calculations, the mechanism of the substrate induced spin reorientation transition in FePc/O-Cu(110) is explained in terms of charge transfer and rearrangement of Fe-3d orbitals. Moreover, we find giant magnetoelectric effects in this system, manifested by the sensitive dependence of its magnetic moment and magnetic anisotropy energy on an external electric field. In particular, the direction of magnetization of FePc/O-Cu(110) is switchable between in-plane and perpendicular axes, simply by applying an external electric field of 0.5 eV/Å along the surface normal.

Giant converse magnetoelectric effect of AlN-(Fe90Co10)78Si12B10 thin film composites

Giant converse magnetoelectric (CME) effect has been found in AlN-(Fe90Co10)78Si12B10 thin film composites fabricated by RF magnetron sputtering on Si/SiO2 substrate. The influence of bias magnetic field Hdc, driven ac voltage Vac and ac frequency f on the CME response of this kind of thin film composites was investigated in detail. The results demonstrated that the AlN-(Fe90Co10)78Si12B10 thin film composites possess a maximum CME coefficient αB of 0.0943mGcm/V at a very low Hdc of 11Oe. It was also observed that the magnetic induction B has an excellent linear relationship to Vac in the range of 1–20V at f=10kHz and Hdc=11Oe. Furthermore, αB responds almost linearly to the ac frequency f from 1.5kHz to 100kHz. These made the heterostructure thin film composites exhibit a promising potential in magnetic and electric field detecting application.

Phase drift of magnetoelectric effect in Terfenol-D/PZT composite materials

Bulk Terfenol-D/PZT composite material with laminated structure is prepared by sticky combination method. The magnetoelectric hysteresis loops under different frequencies are measured and analyzed by new plotting method in the polar coordinates. The results show that tiny phase drift occur in a non-resonant-frequency magnetoelectric hysteresis loop and significant phase drift as large as 90 degrees accompanied with a giant magnetoelectric effect occurs in a resonant-frequency magnetoelectric hysteresis loop. Terfenol-D powder/Epoxy/PZT composite material is prepared by fill method and used as contrast material. Comparison reveals that the phase drift in the non-resonant frequency magnetoelectric hysteresis loop is induced by eddy current in the bulk ferromagnetic constituent, while around the resonant frequency, the significant phase drift is derived from the variation of the elastic property induced by the applying magnetic field.

Giant resonant magnetoelectric effect in bi-layered Metglas/Pb(Zr,Ti)O3 composites

In this paper, giant resonant magnetoelectric (ME) effect in an unsymmetrical bi-layered Metglas/Pb(Zr,Ti)O3 ME composites with multi-push pull configuration that can be significantly tuned was investigated experimentally and theoretically. The actual measured and predicted results present the similar resonant frequency shifting behaviors for such ME composites: The resonant frequency can be varied from 70 Hz to 220 Hz by tip mass loading, where the ME voltage coefficients were over 250 V/cm-Oe. Moreover, the giant frequency-tunable resonant effect allowed us to design a 60 Hz magnetic field energy harvester to be capable of harvesting energy generated by electronic instruments working on a 60 Hz ac power supply.

Investigation of low frequency giant magnetoelectric torque effect

The giant magnetoelectric (ME) effect induced by the coupling of piezoelectricity and magnetic torque in piezo-bimorph/magnet composites has been investigated. The relation between the ME voltage and the sample's geometry (thickness, length, width, etc.), materials parameters (piezoelectric coefficient, residual flux density, permittivity, etc.) was derived through the elasticity mechanics method. Our experimental results confirmed the theoretical prediction. A Pb(Zr1−xTix)O3-bimorph/NdFeB sample with 500pT sensitivity at 10Hz was also constructed and showed a good linearity in the measurement range of nano to mili tesla. This research has provided a guide of designing better magnetoelectric devices with low cost and zero power consumption.

Magnetoelectric Hexaferrites

Magnetoelectric (ME) multiferroics are materials that combine coupled electric and magnetic dipoles. Studies of ME multiferroics are a time-honored research subject because of their potential for future electronic devices. Recent discoveries have revealed that ferroelectricity can be induced by complex internal arrangements of magnetic moments. This new family of multiferroics is called magnetically induced ferroelectrics. Magnetically induced ferroelectrics are known to show giant ME effects, i.e., changes in ferroelectric polarization upon application of an external magnetic field. However, their ME effects usually occur at temperatures that are too low and at applied external fields (> ∼0.1 T) that are too high to be of practical use. Thus, the quest for a robust room-temperature ME effect is a major challenge in ME research. Lately, some ferrites with hexagonal crystal structures, termed hexaferrites, have been found to show ME effects at room temperature and low magnetic fields (∼0.01 T). The results represented an important step toward practical applications using the ME effect in magnetically induced ferroelectrics. This review introduces structure, magnetism, and resulting magnetoelectricity of hexaferrite systems, which are promising candidate materials for ME devices.

Electric-field control of magnetic domain wall motion and local magnetization reversal

Spintronic devices currently rely on magnetic switching or controlled motion of domain walls by an external magnetic field or spin-polarized current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including enhanced functionality and low power consumption. Here we report on an approach to electrically control local magnetic properties, including the writing and erasure of regular ferromagnetic domain patterns and the motion of magnetic domain walls, in CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer from ferroelastic domains in ferroelectric media to continuous magnetostrictive films with negligible magnetocrystalline anisotropy. Optical polarization microscopy of both ferromagnetic and ferroelectric domain structures reveals that domain correlations and strong inter-ferroic domain wall pinning persist in an applied electric field. This leads to an unprecedented electric controllability over the ferromagnetic microstructure, an accomplishment that produces giant magnetoelectric coupling effects and opens the way to electric-field driven spintronics.

Giant magnetoelectric torque effect and multicoupling in two phases ferromagnetic/piezoelectric system

The physical mechanism of a non-magnetostrictive magnetoelectric (ME) effect was revealed and designated as the ME torque (MET) effect. Experimental results showed that the MET effect could be huge; a simple MET device could achieve giant ME voltage coefficients of 100 V/cm.Oe at 1 Hz and 2100 V/cm.Oe at the first order resonant frequency. These are the highest reported ME coefficients in a bulk device ever. We then proposed the multicoupling ME effect, which comes from the interaction of magnetostriction, magnetic torque, and piezoelectricity, and rewrite the ME constitutive tensor equation. The abnormal phenomenon in the (1-3) structure ME thin film that T-L mode might bring larger ME coupling than L-L mode was successfully explained from the multicoupling concept. These researches have extended the giant ME effect from the traditional magnetostrictive/piezoelectric system to a common ferromagnetic/piezoelectric system, and gave more choices to scientists/engineers for constructing the giant ME device.

Concurrent transition of ferroelectric and magnetic ordering near room temperature

Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

Noise Performance of Magnetometers With Resonant Thin-Film Magnetoelectric Sensors

Sensors based on materials with a giant magnetoelectric (ME) effect may be used to measure biomagnetic fields at room temperature. It is necessary to know the noise behavior of the whole detection unit. The noise level of a thin-film ME sensor was measured at room temperature, and suitable types of low-noise amplifiers were investigated. Noise measurements were carried out at room temperature. Results show a sensitivity value of 5.4 pT/ √Hz at a resonance frequency of 330 Hz. Furthermore, the signal-to-noise ratio was investigated in order to improve the sensitivity of the sensor.

Enhanced sensitivity to direct current magnetic field changes in Metglas/Pb(Mg1/3Nb2/3)O3–PbTiO3 laminates

We have developed Metglas/Pb(Mg1/3Nb2/3)O3–PbTiO3 magnetoelectric (ME) laminates that have notably larger ME coefficients, with maximum values of up to 45 V/cm Oe. Based on this giant ME effect, the dc magnetic field sensitivity for Metglas/PMN–PT laminate sensors was improved by a factor of > 3, relative to that for Metglas/Pb(Zr,Ti)O3 (PZT)-based ones of the same geometry. Our new ME sensor can detect dc magnetic field changes as small as (i) 5 nT at 1 kHz and (ii) 1 nT near the resonant frequency in a shield chamber.

Surface Effects on Morin Transition, Exchange Bias, and Enchanced Spin Reorientation in Chemically Synthesized DyFeO3 Nanoparticles

A giant linear magnetoelectric effect was observed by Y. Tokura’s group recently in multiferroic DyFeO3, which demands a detailed investigation of its magnetic properties. Additionally, there is little information on the changes of chemical and physical properties of these materials with the reduction in particle size in spite of the potential applications of these materials in nanoscale devices. As the wet-chemical synthesis of these materials in nanosize and getting a control over crystallinity and stoichiometry is nontrivial and poses a serious challenge prohibiting the study of their size-dependent properties. Here, we report the synthesis of DyFeO3 nanoparticles using a surfactantless hydrothermal method with a detailed magnetic property measurement. The as-synthesized DyFeO3 nanoparticles showed excellent crystallinity with average particle size in the range 50−60 nm. The structural analysis indicated that they are of a distorted orthorhombic pervoskite crystal structure. Detailed dc magnetization m...

Giant magnetoelectric effects in multilayered composites of cobalt ferrite and lead magnesium niobate titanate

The magnetoelectric (ME) coupling responses of [CoFe2O4/(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3]n, represented as (CFO/PMNT)n, multilayered composites were theoretically investigated by using an average method. It is found that a stronger interface coupling could be obtained in multilayers than in bilayers if the number of layers (n) is reasonably increased. Using an empirical dependence of the interface coupling parameter on the number of layers n, it is theoretically estimated that the ME coupling effect is first enhanced and then deteriorated with the gradual increase in n. The best ME response is estimated to occur at n=15, where the transverse ME voltage coefficient αE,31 reaches as high as 658 mV·cm−1·Oe−1. Moreover, it is theoretically found that the ME coupling effect in (CFO/PMNT)n multilayered composites is strongly dependent on the volume fraction of the piezoelectric (or magnetostrictive) phase, and the ME voltage coefficient for transverse field orientation (αE,31) is estimated to be roughly 90% higher than that for the longitudinal case (αE,33), revealing a large anisotropy in the ME coupling effect of (CFO/PMNT)n multilayered composites. These findings pave the way for experimental achievement of strong ME coupling responses, and provide important implications for the design and performance optimization of related devices comprising this kind of multiferroic magnetoelectric materials.

Skyrmion lattices in the BiFeO3 multiferroic

This work examines conditions for skyrmion lattice stability in BiFeO3 multiferroic films possessing record high ferroelectric and antiferromagnetic transition temperatures, giant polarization, and a giant magnetoelectric effect. Using analytical and numerical calculations, we demonstrate stability of solitary spin vortices (skyrmions) and skyrmion lattices in BiFeO3 films owing to the Dzyaloshinskii-Moriya interaction. Our results confirm that BiFeO3 can be used as a matrix for chips with ultrahigh data density, up to 10 Tb/cm2.

A theoretical study of nonlinear magnetoelectric effect in magnetostrictive–piezoelectric trilayer

A novel nonlinear theoretical model is established for magnetoelectric (ME) effect in trilayer of magnetostrictive and piezoelectric phases, in which the nonlinear magnetic-mechanical coupling behavior for the magnetostrictive phase is firstly taken into account. In this theoretical model, the interface coupling parameter k is used for characterizing actual bonding conditions at the interface. The coupled magnetic-mechanical-electric effect involving linear and nonlinear coupling interactions in the ME laminated composites is numerically simulated using this nonlinear model. The numerical results predict giant ME effect for Terfenol-D based ME laminated composites. The quantitative dependences of the giant ME effect on the applied magnetic field, the piezoelectric property of piezoelectric phase, the volume fraction of magnetostrictive phase and the interface coupling parameter k are discussed in details. All of these dependences indicate that the nonlinear theoretical model established in this article can accurately capture nonlinear magnetic-mechanical-electric coupling behavior for Terfenol-D based ME laminated composites. The giant ME effect predicted for the Terfenol-D/PMN-FT/Terfenol-D composites is in excellent agreement with recent experimental data available. It confirms the validity and reliability of the obtained nonlinear theoretical model, and demonstrates the significance and necessity of considering the nonlinear magnetic-mechanical coupling behavior of Terfenol-D. (C) 2010 Elsevier Ltd. All rights reserved.

Low-field magnetoelectric effect at room temperature

The discoveries of gigantic ferroelectric polarization in BiFeO(3) (ref. 1) and ferroelectricity accompanied by a magnetic order in TbMnO(3) (ref. 2) have renewed interest in research on magnetoelectric multiferroics, materials in which magnetic and ferroelectric orders coexist, from both fundamental and technological points of view. Among several different types of magnetoelectric multiferroic, magnetically induced ferroelectrics in which ferroelectricity is induced by complex magnetic orders, such as spiral orders, exhibit giant magnetoelectric effects, remarkable changes in electric polarization in response to a magnetic field. Many magnetically induced ferroelectrics showing the magnetoelectric effects have been found in the past several years. From a practical point of view, however, their magnetoelectric effects are useless because they operate only far below room temperature (for example, 28 K in TbMnO(3) (ref. 2) and 230 K in CuO (ref. 11)). Furthermore, in most of them, the operating magnetic field is an order of tesla that is too high for practical applications. Here we report materials, Z-type hexaferrites, overcoming these problems on magnetically induced ferroelectrics. The best magnetoelectric properties were obtained for Sr(3)Co(2)Fe(24)O(41) ceramics sintered in oxygen, which exhibit a low-field magnetoelectric effect at room temperature. Our result represents an important step towards practical device applications using the magnetoelectric effects.

Giant resonance frequency tunable magnetoelectric effect in a device of Pb(Zr0.52Ti0.48)O3 drum transducer, NdFeB magnet, and Fe-core solenoid

Magnetoelectric (ME) effect has been studied in a device of Pb(Zr0.52Ti0.48)O3 (PZT) drum transducer, NdFeB magnet, and Fe-core solenoid. A unique ME effect is found to originate from the magnetic force-induced effectively amplified piezoelectric effect. Under the application of a magnet with dimensions of ϕ22×7.6 mm2, a giant ME coefficient of 13.2 V/cm Oe and a power density of 16.4 μW∕Oe across a 14 kΩ resistor were obtained at the first order radial resonance frequency of 650 Hz. Importantly, with increasing magnet mass, the resonance frequency decreases, while the resonance ME effect first increases and then decreases, which means a tunable resonance ME effect.

Giant magnetoelectric effect in the Jeff=1/2 Mott insulator Sr2IrO4

Strong spin-orbit, crystal field, and Coulomb interactions compete to drive a narrow-gap Mott state in Sr2IrO4. Our study of the magnetic, thermal, and electrical properties of single-crystal Sr2IrO4 reveals a giant magnetoelectric effect (GME) arising from a frustrated magnetic/ferroelectric state below 240 K. The GME features (1) a strongly enhanced electric permittivity that peaks near a newly observed magnetic anomaly at 100 K, and (2) a large magnetodielectric shift (100%) near a metamagnetic transition.

Giant magnetoelectric effect in magnet-cymbal-solenoid current-to-voltage conversion device

A giant magnetoelectric (ME) effect is reported in a current-to-voltage (I-to-V) conversion device formed by sandwiching a PZT piezoelectric cymbal transducer between an NdFeB magnet and a Fe-core solenoid. The observed ME effect results from the direct coupling of the electromagnetically induced attractive-repellent force effect in the magnet-solenoid assembly with the amplified piezoelectric effect in the cymbal transducer. The device exhibits a colossal I-to-V conversion factor (S) of 27.1 V/A with a giant ME coefficient (αV) of 1.24 V/Oe at a low resonance frequency of 2.33 kHz, besides a large S of 0.74 V/A with a high αV of 34 mV/Oe in the nonresonance frequency range of 40 Hz–1 kHz. A physical model based on the combination of electromagnetomechanics in the magnet-solenoid assembly and amplified piezoelectricity in the cymbal transducer is present to explain the observed ME effect and the resulting I-to-V conversion in the device.

Present status of theoretical modeling the magnetoelectric effect in magnetostrictive-piezoelectric nanostructures. Part II: Magnetic and magnetoacoustic resonance ranges

We presented here the theoretical analysis of high frequency magnetoelectric (ME) effects for a ferrite-piezoelectric bilayer and a detailed treatment for electric field induced resonance field shift for ferromagnetic resonance (FMR) in layered structures. ME effects in a single-crystal ferrite-piezoelectric bilayer in the magnetoelastic resonance region are considered. The theory predicts a giant ME effect at magnetoacoustic resonance. The enhancement in ME effect predicted by our theory arises from interaction between elastic modes and the uniform precession mode, resulting in magnetoelastic modes. The peak ME voltage coefficient appears at the coincidence of acoustic resonance and FMR frequencies. In our calculations, we suppose that the layer thickness is sufficiently large to neglect the influence of strain relaxation on average stresses in the structures that determine the ME voltage coefficient. The work presented here will certainly be of interest for the design and analysis of electrically controlled high-frequency devices. Microwave devices of magnetic type with electrical control have unique advantages over traditional ferrite and semiconductor analogs.