Converse Magnetoelectric Coupling Research Articles

Electric field control of 180° magnetization reversal in a spin-valve multiferroic heterostructure

Electrical tuning of magnetism, rather than a spin current or magnetic field, has attracted much attention due to its great potential for designing energy-efficient spintronic devices. However, pure electric field (E-field) control of 180° magnetization reversal is still challenging. Thus, we report an E-field-controlled 180° magnetization reversal in a spin valve (SV)/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) multiferroic heterostructure. Via the converse magnetoelectric coupling effect in CoFe/PMN-PT heterostructures, the magnetic anisotropy and coercive field of the CoFe film can be tremendously modulated by an E-field. We fabricated an optimized SV grown on the PMN-PT substrate, in which the magnetic moments of the free and pinned layers are parallel to each other at the initial state. By applying an E-field, the coercive field of the free layer was enhanced, exhibiting an antiparallel configuration between the free and pinned layers. Based on the theoretical and experimental results, a complete 180° magnetization reversal of the free layer can be obtained without a magnetic field. Accordingly, an E-field-controlled giant, reversible and repeatable magnetoresistance modulation can be achieved. This work proposes a feasible strategy to achieve E-field-controlled 180° magnetization reversal, which is critical for exploring ultralow power consumption magnetic memory devices.

Tailoring polymer-based magnetoelectrics for spintronics: Evaluating the converse effect

The use of magnetoelectric (ME) materials for switching the magnetization of spintronic devices is highly attractive due to their non-volatility, high-speed operation, reduced heat dissipation, miniaturization, and scalability. Despite the numerous reports in the literature focusing on the evaluation of the direct ME effect, the converse effect remains inadequately studied. This gap in knowledge significantly hinders the development of spintronic-related applications such as magnetic sensors, data storage, quantum computing and environmental/biomedical monitoring devices. Here we demonstrate tailored mechanical (Young's Modulus of 1.2 GPa), electric (conductivity of 3.4 × 10−6 S.m−1, dielectric constant (17 at 1 kHz), magnetic saturation (≈9 emu.g−1); piezoelectric (|d33|=11 pC.N−1), and converse ME (coefficient up to 6.3 mOe.cm.V−1: the highest reported on 1–3 composites and just 1 order of magnitude lower than the ones exhibited by ceramic-based 2–2 composites) properties obtained on P(VDF-TrFE)-based composites produced by solvent-casting. This work not only assesses various magnetostrictive fillers, such as CoFe2O4, Fe3O4, and NdFeB, but also advances the development of low-voltage-induced converse magnetoelectric (ME) coupling essential for high-performance spintronic device applications.

Mutual control of electric and magnetic orders near room temperature in Al doped Y-type hexaferrite single crystals

Realizing robust magnetoelectric (ME) coupling effect near room temperature is still a long-standing challenge for the application of multiferroic materials in next-generation low-power spintronic and memory devices. Here we report a systematic study on the magnetic, dielectric, and ME coupling properties of Y-type hexaferrite Ba0.5Sr1.5Co2Fe12–xAlxO22 (x = 0.0, 0.5, 1.0) single crystals. The Al doping can induce the shifting of the alternating longitudinal conical (ALC)-proper screw (PS) magnetic phase transition temperature from 200 K for x = 0.0 to 365 K for x = 1.0. The most interesting feature is that the Ba0.5Sr1.5Co2Fe11AlO22 single crystal displays a direct and converse ME coupling coefficient with ∼ 3,100 ps/m and ∼ 3,900 ps/m at 250 K, respectively, due to the Al-doped enhanced stability of ALC phase. Moreover, the exchange bias also verifies the strong coupling of electric and magnetic orders. These results provide a valuable insight on the modulation of ALC structure and the mechanism of ME effect in Y-type hexaferrites.

Large room temperature magnetoelectric response in quasi 1–2 nanocomposite films on mica substrate

AbstractA novel quasi 1–2 type magnetoelectric (ME) nanocomposite films composted of one‐dimensional CoFe2O4 nanofibers and two‐dimensional PbZr0.2Ti0.8O3 films on flexible mica substrate have been designed and fabricated. The ME coupling effects have been greatly enhanced due to the release of the clamping effect and the high strain transfer efficiency between the large aspect ratio of the nanofibers and ferroelectric thin films. The release of the clamping effect was confirmed by reducing the thickness of the mica substrate, in which the piezoelectric coefficient and ME coupling coefficient of the nanocomposite films have been greatly boosted by the decrease in the mica thickness. A large direct ME coupling coefficient of 630 mV/(cm Oe) and a converse ME coupling coefficient of 1.43 × 10−8 s/m have been achieved in the quasi 1–2 nanocomposite film with a substrate thickness of 25 µm. Furthermore, the stain‐mediated ME coupling was revealed by magnetic field/electric field‐induced local ferroelectric/magnetic domain switching dynamics.

Electric field tuning of multistate and nonvolatile resistance variation in amorphous Fe75Si25/PMN-0.3PT (0 0 1) heterostructures

The multistate resistance states in the amorphous Fe75Si25/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN − 0.3PT) (001) heterostructure were modulated by electric fields (E). Based on the in-plane nonvolatile stress changes associated with ferroelectric domain switching in PMN-0.3PT, the widening and narrowing of surface gaps, and the fact that magnetism generally tracks the strain variation in amorphous Fe75Si25 films, the distinct four-state and nonvolatile resistance tuning near the coercive E-field are observed. Then, combining the converse magnetoelectric coupling and magnetoresistive effect, we quantify the coaction effect and equivalence relation between the E-field and magnetic fields (H) on the resistance modification. Meanwhile, another four-state resistance is obtained under the coaction of the E-fields and H-fields. All eight resistive states exhibit excellent E-field switchable behavior and stability performance at room temperature. These results provide a promising approach for exploring and designing multistate and multifield controlled spintronic memory devices.

Electric field control of magnetization in polycrystalline ZnO film

A polycrystalline ZnO film is grown on a silicon substrate by the pulsed laser deposition method, and the electric field-induced magnetization in ZnO using an optical cantilever beam magnetometer setup is studied. The magnetization vs bipolar dc electric field measurements reveal the occurrence of magnetization switching in the ZnO film. The magnetization switching in the presence of an electric field is ascribed to the converse magnetoelectric (ME) coupling that takes place between the electrical and the magnetic order parameters existing in the ZnO film. We have found the strain-driven magnetization change as evidenced by the butterfly shape of the magnetization vs the electric field curve. A saturation magnetization of 13.31 MA/m is obtained. Moreover, a significant value of the ME coupling coefficient (α) (1.61 × 10−7 s/m) has also been reported in this article. The emergence of electric field-induced magnetization in a single polycrystalline ZnO film is regarded to be a very promising aspect in designing high-density energy-efficient spintronic and different multifunctional devices.

Visible-light controlled interfacial magnetoelectric coupling in SrRuO3/BaTiO3 heterostructure

Artificial multiferroics provide a tunable magnetoelastic and magnetoelectric coupling owing to the variety of combinations of ferroelectric and ferromagnetic layers, hence facilitate a better perspective for device applications such as magnetic field sensors and electric write magnetic -read memory devices. The intertwined physical properties can be controlled via external parameters such as electric field, temperature, and magnetic field. Here, we report an additional mode to manoeuvre the magnetoelastic and magnetoelectric coupling in an epitaxial SrRuO3/BaTiO3 multiferroic heterostructure using polarized visible light illumination. The light-induced ferroelastic (FE) domain wall motion in underlying BaTiO3 leads to photostriction and photodomain effects. Consequently, the change in the converse magnetoelastic effects leads to modify the magnetic properties of the above grown SrRuO3 layer. Besides this, we have observed a sharp and persistent changes in the SrRuO3/ BaTiO3 heterostructure, when the system is electrically biased owing to the change in the interfacial converse magnetoelectric coupling. Light controlled magnetization tunability in BaTiO3-based artificial multiferroic can open an alternate way for potential applications in several types of wireless devices and magnetic field sensors, electric write magnetic-read memory devices and other interesting optomechanical systems. Our findings in this context can be proven indeed as a novel prospective for opto-spintronics device applications.

Tuning the Performance of Acoustically Actuated Magnetoelectric Antenna via Magnetic and Mechanical Stimuli

Magnetoelectric (ME) antenna operates at the acoustic wave resonance rather than EM wave resonance, thus it shows significant superiority for developing compact antennas and antenna arrays. The simulation of ME antenna involves the nonlinear coupling of Electrostatics, Solid Mechanics, and Magnetic physics, making it difficult to model such devices. This paper proposes a fully multi-field coupled model for the ME antenna, in which the nonlinear magnetostrictive model is taken into account. The nonlinear magnetization is solved and then AC and DC simulations are performed by coupling different physics. The effects of magnetic bias and pre-stress on the converse magnetoelectric (CME) coupling and near-field radiation are discussed for the first time, to regulate the performance of the ME antenna with fixed dimensions. The results indicate that the magnetic bias and pre-stress can change the resonance frequency, CME coefficient, and near-field radiation of ME antenna. Particularly, it should be noted that pre-stress has the opposite effect in the low and high regions of the bias field. The near-field radiation is significantly enhanced by applying a proper magnetic bias or pre-stress. This simulation may facilitate the understanding of nonlinear CME behavior and provide a basis for designing nonlinear active and tunable ME antenna.

A two-dimensional multi-field coupling model for converse magnetoelectric effect in acoustically actuated antennas

The radiation performance of acoustically actuated magnetoelectric (ME) antennas is originated from converse magnetoelectric (CME) effect that converts the electric field to magnetic field due to strain coupling. This paper presents a two-dimensional model for the CME effect of ME antennas with considering a fully magneto-elastic coupled characteristic of magnetostrictive materials. The nonlinear magnetostrictive relation is equivalent to a linear-like form using the equivalent parameter method. The coupled effects of magnetic bias and pre-stress on the CME coupling are discussed. The prediction for the CME coefficient shows a good agreement with the experimental data. The results indicate that pre-stress and magnetic bias have a strong-coupled effect on the CME effect. In addition, optimal loading modes are obtained for improving the CME effect. The radiations of ME antennas have not yet been obtained. Nevertheless, the results in this work may provide a basis for further investigation on the radiations.

Converse magnetoelectric coupling coefficient greater than [formula omitted] s/m in perpendicularly magnetized Co/Pd multilayers on Pb(Mg[formula omitted]Nb[formula omitted])O3-PbTiO3

Multiferroic heterostructures consisting of Co/Pd multilayers on Pb(Mg1/3Nb2/3)O3-PbTiO3(011) substrates are experimentally investigated. The converse magnetoelectric (CME) effect is characterized by anomalous Hall effect measurements with application of an electric field (E). The remanent magnetization state for the [Co(0.8 nm)/Pd(2 nm)] multilayer is significantly modulated by the application of E. The room-temperature CME coupling coefficient (αE) is estimated to be 1.0–1.1 × 10−6 s/m, which is the largest among those of multiferroic heterostructures with perpendicular magnetic anisotropy.

Evidence of direct and converse magnetoelectric coupling in eco-friendly 0.75(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)–0.25(CoFe2O4) particulate composite

Magnetoelectric (ME) multiferroic composite exhibits the ME effect, and their interaction between piezoelectric and magnetic phase is measured in terms of ME coupling (α). ME coupling is an interesting and characteristic property of ME materials and can be evaluated by direct and indirect methods. In this work, the solid-state sintering technique has been adopted to synthesize the lead-free 0.75(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)–0.25CoFe2O4 (NBBT-CFO) composite. The X-ray diffraction patterns and uniform distribution of closely packed grains reveal the coexistence of constituent phases in the composite. This composite reveals room-temperature multiferroic properties. The room temperature dielectric constant (ε′) of the poled sample displays the resonance and anti-resonance peaks at a particular frequency ∼ 455 kHz and 450 kHz, respectively. The estimated value of the electromechanical coupling coefficient (kP) is 16.69%. The direct ME and converse ME coupling study has been done through the Polarization (P) vs Electric field (E) and Magnetization (M) vs Magnetic field (H) hysteresis loop measurements of magnetically and electrically poled and unpoled samples, respectively. The variation in the polarization and magnetization value reveals the presence of direct and converse ME coupling in the composite.

Strain and electric field control of magnetic and electrical transport properties in a magnetoelastically coupled Fe3O4/BaTiO3 (001) heterostructure

We present a study of the control of electric field induced strain on the magnetic and electrical transport properties in a magneto-elastically coupled artificial multiferroic Fe3O4/BaTiO3 heterostructure. In this Fe3O4/BaTiO3 heterostructure, the Fe3O4 thin film is epitaxially grown in the form of bilateral domains, analogous to a-c stripe domains of the underlying BaTiO3(001) substrate. By in-situ electric field dependent magnetization measurements, we demonstrate the extrinsic control of the magnetic anisotropy and the characteristic Verwey metal-insulator transition of the epitaxial Fe3O4 thin film in a wide temperature range between 20-300 K, via strain mediated converse magnetoelectric coupling. In addition, we observe strain induced modulations in the magnetic and electrical transport properties of the Fe3O4 thin film across the thermally driven intrinsic ferroelectric and structural phase transitions of the BaTiO3 substrate. In-situ electric field dependent Raman measurements reveal that the electric field does not significantly modify the anti-phase boundary defects in the Fe3O4 thin film once it is thermodynamically stable after deposition and that the modification of the magnetic properties is mainly caused by strain induced lattice distortions and magnetic anisotropy. These results provide a framework to realize electrical control of the magnetization in a classical highly correlated transition metal oxide.

Giant converse magnetoelectric effect in a multiferroic heterostructure with polycrystalline Co2FeSi

To overcome a bottleneck in spintronic applications such as those of ultralow-power magnetoresistive random-access memory devices, the electric-field control of magnetization vectors in ferromagnetic electrodes has shown much promise. Here, we show the giant converse magnetoelectric (CME) effect in a multiferroic heterostructure consisting of the ferromagnetic Heusler alloy Co2FeSi and ferroelectric-oxide Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) for electric-field control of magnetization vectors. Using an in-plane uniaxial magnetic anisotropy of polycrystalline Co2FeSi film grown on PMN-PT(011), the nonvolatile and repeatable magnetization vector switchings in remanent states are demonstrated. The CME coupling coefficient of the polycrystalline Co2FeSi/PMN-PT(011) is over 1.0 × 10−5 s/m at room temperature, comparable to those of single-crystalline Fe1-xGax/PMN-PT systems. The giant CME effect has been demonstrated by the strain-induced variation in the magnetic anisotropy energy of Co2FeSi with an L21-ordered structure. This approach can lead to a new solution to the reduction in the write power in spintronic memory architectures at room temperature.

Investigation of magnetic properties and converse magnetoelectric effect in the composite of doped barium hexaferrite with potassium niobate, 0.5BaFe10Sc2O19-0.5KNbO3 and 0.5BaFe10In2O19-0.5KNbO3

This study investigates the magnetic and electric properties of the 0.5BaFe 10 Sc 2 O 19 -0.5KNbO 3 (0.5BFSc2O-0.5KNO) and 0.5BaFe 10 In 2 O 19 -0.5KNbO 3 (0.5BFIn2O-0.5KNO) composite samples. Refined X-ray diffraction (XRD) studies substantiate the presence of both ferrimagnetic (BFSc2O and BFIn2O) and ferroelectric KNbO 3 phase with the ratio (0.5:0.5) in both the compounds without any impure phase. By electric poling the samples with an electric field of 2.5 kV/cm, magnetization shows a different behaviour (decreasing in Sc and increasing in doped composite), can be attributed to the electric field induced changes of spin states due to stress induced at the interface of ferrimagnetic (FM)/ferroelectric (FE) regions. Strong converse magnetoelectric coupling (CME) was observed in both the compounds, with a large electric field modulation in magnetism (80%) in the 0.5BFInO-0.5KNO composite. Dielectric studies reveal the presence of ferroelectric ( FE-T c ) transition around the magnetic Curie temperature ( FM-T c ) of respective composites, further indicates the presence of converse magnetoelectric coupling in both systems. • Magnetic and magnetoelectric properties of the composite of doped barium hexaferrite with potassium niobate are studied. • Refined XRD show both ferroelectric KNbO3 and ferrimagnetic BaFe10Sc2O19 and BaFe10In2O19 phases present with a 50:50 ratio. • DC magnetization shows different doping element in the ferrites leads to different magnetic behaviour after electric poling. • Converse magnetoelectric coupling of 45% in 0.5BaFe10Sc2O19-0.5KNbO3 and 80% in 0.5BaFe10In2O19-0.5KNbO3 was observed. • Dielectric studies show the ferroelectric transition around their respective magnetic Curie temperature in both the systems.

Impact of electric poling on structure, magnetism and ferroelectricity of 0.7PbFe0·5Nb0·5O3 -0.3BiFeO3 multiferroic

In this paper we have discussed the impact of electric poling on structure, magnetism and ferroelectricity of 0.7PbFe0·5Nb0·5O3 - 0.3BiFeO3 (PBFN) multiferroic. Magnetization data exhibit the presence of strong converse magneto electric coupling in a material. The temperature dependent Raman measurements demonstrate considerable changes in Raman scattering intensity and spectrum structure around TC, indicating a structural change around TC. The octahedral stretching vibration modes revealed a remarkable frequency shift below TN and the anomalies are owing to the coupling interaction between the spin-phonons. Changes in Raman modes and magnetization data support the hypothesis of converse magnetoelectric coupling. By poling, the improvement in ferroelectric domain ordering occurs and it was confirmed by P-E loops. We present the implications of our investigation on electric poling of PBFN multiferroic in the current interest of spintronics.

Magnetoelectric response and internal friction in two-layer ceramic composites based on Mn0.4Zn0.6Fe2O4 magnetostrictor and PbZr0.53Ti0.47O3 piezoelectric

Magnetoelectric (ME) and anelastic properties of two-layer ceramic composites based on Mn0.4Zn0.6Fe2O4 magnetostrictor and PbZr0.53Ti0.47O3 piezoelectric at DC magnetic field strengths of 0–220 Oe, temperatures of 293–393 K, and volume fractions of PbZr0.53Ti0.47O3 of 0.40–0.67 were studied. It was found that a converse ME coupling coefficient α31 increases with the DC magnetic field strength Н1, passes through a maximum with the volume fraction ν, and decreases as temperature T rises. Dependences of α31 on Н1, ν, and T are explained using a model of effective parameters of a heterogeneous medium. The inverse correlation is revealed between α31 and an internal friction at resonant frequencies. Dependences of the internal friction on Н1, ν, and T are associated with the interaction of ferroelectric domain boundaries with crystal-lattice defects.

Voltage-controlled three-state magnetic memory based on anisotropic magnetoresistance in a multiferroic heterostructure

An energy efficient technique has shown to produce a three-state magnetic memory cell in a [011]-poled Ni80Co20/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) heterostructure. Via the magnetic field deposition, a 45° magnetic easy axis of the NiCo film was induced in the film plane. By using a strong converse magnetoelectric coupling between the NiCo film and the PMN-PT, the magnetic moments of NiCo can be modulated to [001] and [1-10] directions of PMN-PT by selecting an appropriate electric field (E-field). Consequently, large, medium, and small anisotropic magnetoresistance (AMR) values are obtained by fixing a measuring current along the [001] direction. The required E-field significantly reduces due to the initial direction of NiCo along the 45° direction. The tunability of the AMR ratio is as large as ∼87%. These results indicate that an energy efficient approach to generate magnetic storage by using only a small E-field rather than a magnetic field with a high energy consumption was realized. This work shows great potential for the development of ultra-low power and high-density magnetoresistive memory devices.

A comparison of converse magnetoelectric coupling effect of YIG film on FE and AFE ceramic substrates

The magnetoelectric properties of laminated heterostructures consisting of ferromagnetic yttrium iron garnet (YIG) films deposited on antiferroelectric (AFE) (Pb0.97La0.02)(Zr0.6Sn0.3Ti0.1)O3 (PLZST) and on ferroelectric (FE) 0.75Pb(Mg1/3Nb2/3)O3-0.25Pb(Zr0.48Ti0.52)O3 (PMN-PZT) ceramics are compared in this work. In particular, the Converse Magneto Electric (CME) coefficient is evaluated for these two types of structures. When the electric field is applied on an AFE ceramic, the CME coefficient peaks at the switching field and, without bias magnetic field, the maximum value is 11.6 × 10−8 s/m. In case of a FE ceramic, at the electric coercive field, the CME coefficient can reach 17 × 10−8 s/m at 0 Oe. Each structure has advantages and disadvantages depending on the applications.

Engineering Resonance Modes for Enhanced Magnetoelectric Coupling in Bilayer Laminate Composites for Energy Harvesting Applications

The magnetoelectric (ME) effect in composites, a strain-mediated coupling phenomenon between piezoelectric and magnetostrictive phases, has a wide range of technological applications. Here, ME coupling phenomena are explored in $\mathrm{Pb}$-free piezoelectric, $0.5\mathrm{Ba}({\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}){\mathrm{O}}_{3}\text{\ensuremath{-}}0.5({\mathrm{Ba}}_{0.7}{\mathrm{Ca}}_{0.3}){\mathrm{Ti}\mathrm{O}}_{3}$ and piezomagnetic ${\mathrm{Ni}\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ bilayer laminate composites. The direct and converse ME coupling strengths are found to be enhanced at the electromechanical resonance modes, rather than at the off-resonance frequencies. Here, it is proposed to further enhance the ME coupling strength at electromechanical resonance modes by the in-phase superimposition of the radial and second bending modes via varying the bilayer thickness, which, in turn, varies the volume fraction of the bilayer. The proposed enhanced ME coupling is experimentally demonstrated at a theoretically envisaged bilayer thickness of about 1.8 mm. This results in a large direct ME coupling coefficient of $22.5\phantom{\rule{0.1em}{0ex}}\mathrm{V}\phantom{\rule{0.1em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.1em}{0ex}}\mathrm{O}{\mathrm{e}}^{\ensuremath{-}1}$, which is around 100% more than the values observed at individual resonance modes. The results are further validated by calculations from theoretical models. The method adopted in this work gives a roadmap to the significant enhancement of the ME effect in laminate composites.

Anomalous Magnetoelectric Coupling Effect of CoFe2O4–BaTiO3 Binary Mixed Fluids

We report an anomalous magnetoelectric coupling effect of CoFe2O4–BaTiO3 binary mixed fluids, which were prepared by distributing surfactant treated (oleic acid) magnetic CoFe2O4 and ferroelectric BaTiO3 nanoparticles into highly insulating base fluid (silicone oil). A strong coupling effect in this mixed fluid has been observed, in which both the remnant polarization/magnetization and coercive electric/magnetic field are found to be enhanced visibly in the presence of an external magnetic/electric field. Colossal converse and direct magnetoelectric coupling coefficients are estimated to be αH = 1.22 × 10–4Oe·cm/V and αE = 2.52 × 104 V/(cm·Oe), respectively. Moreover, this coefficient clearly depends on the volume fraction of the two kinds of particles and the applied external magnetic/electric field. Even more amazing, CoFe2O4 also shows a strong magnetoelectric coupling effect with a coefficient as high as 4.2 × 10–5 Oe·cm/V. Further analysis indicates that the aggregated, chain-like structure of the pa...