Magnetoelectric Coefficient Research Articles

Emergence of magnetic order and enhanced magnetoelectric coupling in Lu-doped Sm2BaCuO5

The green-phase compound Sm2BaCuO5 has recently drawn significant attention due to the prominent linear magnetoelectric (ME) coupling effect. Herein, we report a successful chemical doping control of magnetic order and ME effect in Lu3+-doped multiferroic Sm2BaCuO5. Upon a small amount of Lu3+ doping, it is suggested that the majority of Cu ions interact through Sm3+ and order at TN1 ∼ 23 K, whereas some Cu2+ interacting through Lu3+ can lead to another transition at T* ∼21 K–16 K upon doping Lu3+ ions from 5% to 20%. More interestingly, this emergent magnetic order is concomitant with a broad valley in the pyroelectric current and dielectric anomaly, providing clear evidence of intrinsic coupling between magnetic and ferroelectric orders. In contrast to the parent phase, significant enhancement of the linear ME coefficient is obtained. Our results unveil the importance of interplay of 4f-3d magnetic interactions in inducing ferroelectricity and offer an alternative route to achieve high performance in ME coupling.

Low magnetic-field induced high temperature dynamic magnetoelectric coupling performances in Z-type Sr3Co2Fe24O41

Magnetic-field induced dynamic magnetoelectric coupling effects and polarization performance of Z-type Sr3Co2Fe24O41 (SCFO) ceramic has been investigated. Results found that SCFO’s transverse tapered magnetic structure can induce electric polarization, and its electric polarization direction will not change under external magnetic effects. First-order dynamic magnetoelectric coupling coefficient (α) and second-order dynamic magnetoelectric coupling coefficient (β) of SCFO exhibited strong response main in magnetic structural phase transition region. The magnetoelectric structural phase transition position appeared in low magnetic field, and the magnetic moment vector and its corresponding electric polarization vector of SCFO exhibited the most unstable state near its equilibrium position, which is beneficial for inducing strong dynamic magnetoelectric coupling response. When the applied magnetic fields to SCFO increased, the magnetic moment stability near the equilibrium position increased, and the dynamic magnetoelectric coupling response decreased. Results showed that the dynamic magnetoelectric coupling response of SCFO can bear T 1 = 370 K high temperature. The dynamic magnetoelectric coupling response induced by low magnetic fields in SCFO contributes to its actual application in next generation magnetoelectric information storage devices.

Magnetoelectric effect in a flexible heterostructure comprising magnetostrictive fiber composite and piezopolymer PVDF

Linear and nonlinear magnetoelectric (ME) effects in flexible composite heterostructures comprising layers of magnetostrictive fiber composite (MFC) and poly(vinylidene fluoride) (PVDF) piezopolymer have been observed and investigated. MFC consists of a set of Ni-wires with a diameter of 100, 150, or 200 μm arranged in parallel close to each other in one layer and placed in a polymer matrix. The structure was excited by an ac magnetic field in the frequency range of 1–15 kHz and simultaneously magnetized in the plane by a dc field H. The voltage generated by the PVDF layer was recorded at the frequency of the structure bending resonance. The ME coefficient of 5.8 V/(Oe cm) was obtained for a heterostructure with Ni-wires 150 μm in diameter at a frequency of 5.1 kHz when magnetized along the wires. The ME effect magnitude depends on the H-field orientation relative to the Ni-wires due to the magnetostriction anisotropy arising from demagnetization effects. The generation of ME voltage second harmonic with an efficiency of 26 mV/(Oe2·cm) was observed in the heterostructure with an increase in the excitation field.

Magnetoelectric effect in Ni[formula omitted]ZnxFe2O4/PZT thin film heterostructures

Magnetoelectric coupling effect of Ni1-xZnxFe2O4/PZT (NZFO/PZT) thin film heterostructures is investigated by tuning the Zn content in NZFO film. The highest magnetoelectric coupling coefficient of NZFO/PZT heterostructures is achieved at x=0.15 with the value of 328 mV/cm Oe. This various magnetoelectric effect in NZFO/PZT heterostructures with different Zn content is induced by distinct magnetostriction of NZFO film, which is related to piezomagnetic coefficient q and the initial permeability μi of NZFO layer, as well as the exchange interaction of ions at tetrahedral and octahedral sites. This study is of helpful for understanding the magnetoelectric effects of epitaxial magnetoelectric heterostructures that involves NZFO ferrite films.

Voltage Control of Perpendicular Magnetic Anisotropy in Multiferroic Composite Thin Films under Strong Electric Fields.

"Ferroelectric/ferromagnetic" multiferroic composites with perpendicular magnetic anisotropy (PMA) are useful for developing power-efficient magnetic memories. Voltage control of PMA has been demonstrated in bulk multiferroic composites based on ferroelectric single crystals, but they are not compatible for integration. Multiferroic composite thin films are useful for developing integrated devices; however, voltage control of PMA in them has not been achieved yet at room temperature due to their low magnetoelectric (ME) coupling coefficient. Here, we demonstrate such functionality and propose to enhance their ME coupling effect under a strong electric field by taking full advantage of the large dielectric strength of ferroelectric thin films. First, the thickness-dependent breakdown of Pb(Zr0.384Ti0.576Nb0.04)O3 (PNZT) thin films was studied, and the two-layer (∼200 nm) samples exhibited the highest breakdown strength (3.68 MV/cm) and small surface roughness (<1 nm). Second, we fabricated "PNZT/(Co/Pt)5" thin films with strong PMA whose breakdown strength is nearly independent of the top electrode materials. Finally, voltage-induced effective magnetic field (Heff) in "PNZT/(Co/Pt)5" was studied. It is comparable to that achieved in bulk composites and will induce magnetization switching under strong electric fields. Multiferroic composite thin films with large breakdown strength will provide a useful platform for enabling integrated multiferroic devices.

Fine-grained magnetoelectric Sr0.5Ba0.5Nb2O6–CoFe2O4 composites synthesized by a straightforward one-pot method

Magnetoelectric (Sr0.5Ba0.5Nb2O6)1−x−(CoFe2O4)x (x = 0.2–0.6) composites were prepared by a one-pot soft-chemistry synthesis using PEG400. Calcining at 700 °C resulted in nanocrystalline composite powders (dcryst. = 24–30 nm) which were sintered between 1050 and 1200 °C to ceramic bodies with relative densities up to 98%. SEM investigations confirm the formation of composite ceramics with a 0–3 connectivity and variable grain sizes from 0.2 to 3.6 μm for sintering up to 1150 °C, while sintering at 1200 °C leads both to a change in the microstructure and a considerable grain growth. Magnetic measurements at 300 K reveal ferrimagnetic behaviour with saturation magnetization values smaller than bulk CoFe2O4 and coercivities between 790 and 160 Oe. Temperature-dependent impedance spectroscopy showed that the relative permittivities decrease both with rising frequency and CoFe2O4 fraction. The frequency dependence of the impedance can be well described using a single RC circuit. Magnetoelectric measurements show the presence of pronounced field hystereses. The maximum magnetoelectric coefficient (αME) depends both on the CoFe2O4 fraction (x) and sintering temperature. The composite with x = 0.3 exhibits the largest αME value of 37 μV Oe−1 cm−1 (@ 900 Hz). With rising frequency of the AC driving field αME increases up to 300–400 Hz and is nearly constant until 1 kHz.

Modulation of magnetoelectric coupling through systematically engineered spin canting in nickel–zinc ferrite

AbstractA nickel–zinc ferrite system, which is one of the well‐known versatile soft‐ferromagnetic oxides, was investigated in terms of magnetoelectric (ME) coupling at room temperature. Herein, we demonstrated that spin canting is manipulated through a composition‐induced structural transition from an inverse to a normal spinel structure, leading to modulation in the ME coupling. The ME coefficient was maximized at 60 at.% Zn substitution with a value of 0.1 mV/(Oe·cm), denoting ∼70% enhancement compared to that of the pure nickel ferrite. It was revealed that the interspin angle is enhanced along the octahedral site at up to ∼60 at.% Zn substitution, consistent with the composition level at the culmination of the ME coupling, evidenced by X‐ray diffraction profiles and magnetic hysteresis loops combined with density functional theory calculations. Given that this approach is based on a tractable fabrication method, this study is expected to be widely used in modulation of the ME coupling in spinel‐structured oxides.

A Sandwich Metal-Insulation-Metal Composite for Magnetoelectric Memory: Experiment and Modeling.

Driven by the development of internet technology, higher requirements on information materials and data storage devices were demanded. To improve the work efficiency and performance of the new generation of information materials and data storage devices, the magnetoelectric (ME) coupling and storage mechanism of magnetoelectric composites deserve more attention. Here, we explored the influence of applied magnetic fields on the output voltage on a metal–insulation–metal (MIM) sandwich composite for realizing the magnetoelectric memory by experiments and modeling. It is found that the DC magnetic field (Hdc) and the output voltage of the polyvinylidene fluoride film are linearly correlated. At a frequency of 1 kHz, the magnetoelectric voltage coefficient is 60.71 mV cm–1 Oe–1, which is evidently larger than that of other film materials. From this work, we can conclude that the MIM sandwich composite could generate higher magnetoelectric voltage under the AC magnetic field (Hac) with higher frequency, which could be used as the magnetoelectric memory device, and provides significant support for improving the performance of magnetoelectric memory devices and the whole internet system.

Room-temperature large magnetoelectricity in a transition metal doped ferroelectric perovskite

There is increasing interest in novel magnetoelectric (ME) materials that exhibit robust ME coupling at room temperature (RT) for advanced memory, energy, spintronics, and other multifunctional device applications, by making use of the ability to control polarization with a magnetic field and/or magnetization via an electric field. Obtaining ME materials with strong ME coupling, understanding the origin, and manipulating its processing along with composition to realize large ME coefficients at RT constitute an important step in multiferroic research. To address this, we have investigated the multiferroic and ME properties of Ni-doped $\mathrm{Pb}({\mathrm{Zr}}_{0.20}{\mathrm{Ti}}_{0.80}){\mathrm{O}}_{3}$ (PZT). We find that the ferroelectric $({T}_{\mathrm{C}}\ensuremath{\sim}700\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ and weak ferromagnetic (\ensuremath{\sim}602 K) phase transitions of Ni-doped PZT are well above room temperature (RT), leading to a strong ME coupling coefficient (${\ensuremath{\alpha}}_{E,31}$) of $11.7\phantom{\rule{0.16em}{0ex}}\mathrm{mV}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{--1}\phantom{\rule{0.16em}{0ex}}{\mathrm{Oe}}^{--1}$ (${H}_{\mathrm{ac}}=1\phantom{\rule{0.16em}{0ex}}\mathrm{Oe}$ and $f=1\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$). While x-ray diffraction suggests a single-phase material, high-resolution transmission electron microscopy reveals regions with and without Ni present; thus magnetoelectric coupling between two phases is possible. First-principles calculations suggest the $(\mathrm{N}{\mathrm{i}}_{\mathrm{Pb}}{)}^{\ifmmode\times\else\texttimes\fi{}}$ defect is likely to be responsible for the experimental observed magnetism and ME coupling in Ni-doped PZT. We further demonstrate that Ni-doped PZT exhibits low loss tangent, low leakage current, large saturation polarization, and weak ferromagnetism. Ultimately, our work demonstrates that Ni-doped PZT is a cost-effective RT multiferroic with strong ME coupling.

Study of enhanced magnetoelectric coupling behavior in asymmetrical bilayered multiferroic heterostructure with two resonance modes

The resonant enhancement of the magnetoelectric coupling effect due to the bending and length modes had been investigated in the asymmetrical bilayered heterostructure consisting of the La0.7Sr0.3MnO3 and BaTiO3 deposited on SrTiO3. The frequency-dependent transverse magnetoelectric voltage coefficient demonstrated two sharp peaks in the vicinity of electromechanical resonant frequencies, which were attributed to the bending and length vibration modes, respectively. The value of the magnetoelectric voltage coefficients for the first peak was higher than that of the second one, which ascribed to the phase shift between the excited magnetic field and induced dielectric polarization. This result demonstrated the asymmetrical bilayered heterostructure has dramatically enhanced magnetoelectric effect when operated near these frequencies, which is likely to provide a tremendous opportunity for configuring the corresponding devices.

Magnetoelectric, magnetodielectric and magneto-impedance couplings in Bi1−xNdxFe0.99Co0.01O3 compounds

In this work Bi1−xNdxFe0.99Co0.01O3 ceramics compositions were synthesized for x = 0.05, 0.20 and, y = 0.01. Structural refinement results show that most of the samples crystallized in a rhombohedral symmetry with R3c. Measurements magnetoelectric coefficient, show that the magnetoelectric coefficients are of second order. The electrical impedance characterization of in function external magnetic fields, has a relative variation of the real dielectric response, the loss tangent and the electrical impedance. The systems, as the DC magnetic field strength increased a gain in both the values of the dielectric constant variation, as well as the variation of the electrical impedance. In other words, the greater the intensity of the magnetic field, the greater your response. There were also significant variations with of the magnetic field AC.

The effect of thickness-dependent strain relaxation on magnetoelectric behaviors for highly c-axis oriented BiFeO3 films on Si substrate

The thickness-dependent strain-relaxation behavior and the associated impacts upon the magnetic, electric properties and magnetoelectric coupling effect for the highly c-axis oriented BiFeO3 (BFO) film films grown on (001) oriented Si substrate were studied. The result shown that the value of remnant polarization and coercive field were suppressed as the strain relaxes with increasing thickness. The BFO films also presented typical weak ferromagnetic hysteresis loops with a low coercive field and small remnant magnetization, and the saturated magnetization and remnant magnetization decreasing with increasing film thickness. The room temperature dynamic magnetoelectric coupling was approved by the transverse magnetoelectric voltage coefficients, which also decreased with strain relaxation due to the increase of thickness, and the maximum was around 265 mV/cm.Oe when the film thickness is 50 nm.

The origin of the large magnetoelectric coupling in the ceramic Ba0.1Bi0.9(Ti0.9Zr0.1)0.1Fe0.9O3

57Fe Mössbauer spectrometry and x-ray powder diffraction are conducted to examine the structure and the local magnetic order at the level of Fe sites of Ba0.1Bi0.9(Ti0.9Zr0.1)0.1Fe0.9O3 ceramic. The Mössbauer spectra in the temperature range of 77 K–623 K were analyzed using a discrete distribution of hyperfine field, indicating that the Néel temperature T N was about 603 K. The ceramic Ba0.1Bi0.9(Ti0.9Zr0.1)0.1Fe0.9O3 remains stable in the rhombohedral structure (R3c) in the temperature range of 300 K–800 K. The anomaly of volume below T N, as detected from the model Debye–Gruneissen, reveals the presence of magnetoelastic coupling in this compound. The total polarization (P) obtained from Rietveld refined atomic positions is found to depend on the magnetic order that leads to the decrease of the total polarization (P) through the anomaly volume. The reduction in the polarization by ΔP ∼ −2.4 μC cm−2 suggests negative magnetoelectric interaction. The total polarization (P) obtained from Rietveld refined atomic is coupled with the magnetic ordering mediated by magnetoelastic coupling. The hyperfine field (B hf) dependence of polarization (P) at a temperature range below T N exhibits a linear evolution, confirming the linear magnetoelectric coupling. At room temperature, the linear magnetoelectric coefficient is about α ME ≈ 1.84 × 10−9 s m−1.

Electric Field Tuning of Magnetism in Fe3O4/Pt/PZN-PT Heterostructures Prepared by Atomic Layer Deposition

Tuning of magnetic properties by electric field (E-field) has received extensive attentions because it is compact, fast, and energy efficient. Here, multiferroic heterostructures of Fe3O4/Pt/PZN-PT (011) (lead zinc niobate-lead titanate single piezoelectric substrate) were in situ fabricated by atomic layer deposition (ALD) using C10H10Fe and O2 as precursors at a low temperature (400 °C) without a subsequent annealing process in H2 atmosphere, which is beneficial in combining with traditional silicon-based semiconductor technology. The E-field dependence of the magnetic anisotropy was studied systematically by ferromagnetic resonance spectroscopy with the larger tunable in-plane magnetic anisotropy of 152 Oe and 318 Oe obtained along the [100] and [0–11] axes, corresponding to the largest magnetoelectric coupling coefficient of 31.8 Oe.cm/kV. Also, the tunable out-of-plane magnetic anisotropy of 35 Oe was obtained along the [011] axis. The outstanding E-field tuning magnetism in the Fe3O4/Pt/PZN-PT heterostructures offers significant possibilities for novel multiferroic devices.

Low-Frequency Magnetoelectric Effects in Magnetostrictive–Piezoelectric Bilayers: Longitudinal and Bending Deformations

A model for the low-frequency magnetoelectric (ME) effect that takes into consideration the bending deformation in a ferromagnetic and ferroelectric bilayer is presented. Past models, in general, ignored the influence of bending deformation. Based on the solution of the equations of the elastic theory and electrostatics, expressions for the ME voltage coefficients (MEVCs) and ME sensitivity coefficients (MESCs) in terms of the physical parameters of the materials and the geometric characteristic of the structure were obtained. Contributions from both bending and planar deformations were considered. The theory was applied to composites of PZT and Ni with negative magnetostriction, and Permendur, or Metglas, both with positive magnetostriction. Estimates of MEVCs and MESCs indicate that the contribution from bending deformation is significant but smaller than the contribution from planar deformations, leading to a reduction in the net ME coefficients in all the three bilayer systems.

PMN-PT/NFO magnetoelectric characterization and the advantages of the dynamic stress magnetization model

Magnetic, electric, and magnetoelectric properties of the Pb(Mg1/3Nb2/3)O3-PbTiO3 and NiFe2O4 multiferroic composite with 80/20 mol percentage ratio were investigated experimentally. Results identify the interplay between the magnetostrictive and piezoelectric phases as the origin of the observed magnetoelectric coupling. Such behavior was then analyzed in light of the square and dynamic stress magnetization models with the latter shown as the better alternative to describe the composite's magnetoelectric coefficient.

Progress in the Development of Single-Phase Magnetoelectric Multiferroic Oxides

Magnetoelectric (ME) multiferroics manifesting the coexistence and the coupling of ferromagnetic and ferroelectric order are appealing widespread interest owing to their fascinating physical behaviors and possible novel applications. In this review, we highlight the progress in single-phase ME multiferroic oxides research in terms of the classification depending on the physical origins of ferroic properties and the corresponding examples for each case, i.e., material by material, along with their ME multiferroic properties including saturation magnetization, spontaneous polarization, (anti)ferromagnetic/ferroelectric transition temperature, and ME coefficient. The magnetoelectrically-active applications of high expectancy are presented by citing the representative examples such as magnetoelectric random-access-memory and multiferroic photovoltaics. Furthermore, we discuss how the development of ME multiferroic oxides should proceed by considering the current research status in terms of developed materials and designed applications. We believe that this short review will provide a basic introduction for the researchers new to this field.

Magnetoelectric and Multiferroic Properties of BaTiO3/NiFe2O4/BaTiO3 Heterostructured Thin Films Grown by Pulsed Laser Deposition Technique

Development of lead-free BaTiO3/NiFe2O4/BaTiO3 (BTO/NFO/BTO) trilayer structure thin films is significant for the realization of eco-friendly and implantable microelectromechanical systems (MEMS)-based devices. In the present work, we report BTO/NFO/BTO trilayer structure as a representative ferroelectric/ferromagnetic/ferroelectric (FE/FM/FE) system deposited on Pt(111)/TiO2/SiO2/Si using Pulsed Laser Deposition (PLD) technique. We report the ferroelectric, magnetic, and ME properties of BTO/NFO/BTO trilayer nanoscale heterostructure having dimensions 140/80/140 nm, at room temperature. High room temperature dielectric constant ~2145 at 100 Hz with low dielectric loss ~0.05 at 1 MHz is observed. Further, the deposited (BTO/NFO/BTO) tri-layered thin films showed magnetoelectric, multiferroic behavior with remanent polarization of 8.63 μCcm−2 at about 0.25 MV/cm and a reasonably high saturation magnetization of ~16 emu/cm3 at ~10 kOe is witnessed at room temperature. Tri-layered films have shown interesting magnetoelectric (ME) coupling coefficient (αE) ~54.5 mV/cm Oe at room temperature.

Component fraction effect on microstructure and properties of CoFe2O4−K0.5Na0.5NbO3 composites

AbstractCoFe2O4−K0.5Na0.5NbO3 (CFO−KNN) composites were sintered in air at 1100°C for 2 h. The relative density of sintered CFO−KNN varied with the KNN/CFO ratio and when the volume fraction of KNN reached 50% or more, the sintered composites had a relative density higher than both of the components (i.e., individually sintered KNN and CFO). The highest relative density (94%) was obtained with the composites of 80 vol% KNN. Transmission electron microscopy did not observe any secondary phase at the interface between CFO and KNN grains. However, elemental analyses showed traces of interdiffusion of Na, K, Co, and Fe ions, which were within the solubility limit of both lattices so that no segregation of other phase occurred. Nevertheless, the interdiffusion altered grain growth kinetics for both phases, resulting in the changes in grain sizes for both KNN and CFO in the composites. The composites of higher CFO content showed lower piezoelectric d33 due to a higher DC conductivity that resulted in an incomplete poling of samples. The attainable magnetoelectric voltage coefficient was 3.6 mV cm−1 Oe−1, which was measured with the composites of 50 vol% KNN.

Phase transitions and magneto-electric properties of 70 wt. % Pb(Fe0.5Nb0.5)O3–30 wt. % Co0.6Zn0.4Fe1.7Mn0.3O4 multiferroic composite

Here, we have studied the phase transition and magneto-electric properties of a 70 wt. % Pb(Fe0.5Nb0.5)O3–30 wt. % Co0.6Zn0.4Fe1.7Mn0.3O4 (70 wt. % PFN–30 wt. % CZFMO) multiferroic composite that exhibits a maximum magneto-electric (ME) coefficient of 26.78 mV/cm Oe at room temperature. Raman analysis confirms the formation of composite and development of strain with the shifting of Raman modes. The local symmetry breaking of end members of the composite is observed by the splitting of Raman modes. The first-order derivative of magnetization with temperature (dM/dT vs T) shows anomalies across 140 K due to the PFN phase, whereas the anomaly around 250 K is due to the spin glass transition of the CZFMO phase. The magnetization vs magnetic field (M–H) study at different temperatures reveals the existence of superparamagnetic behavior above 300 K. The temperature-dependent dielectric behavior of the composite shows an anomaly around ferroelectric phase transition (Tm) for the PFN phase along with the broad relaxation peak arising due to the CZFMO phase. The linear behavior of magnetocapacitance (MD%) with the square of magnetization (M2) suggests the existence of biquadratic ME coupling. The ME study on the composite suggests the existence of both direct and converse ME effects.