High Magnetoelectric Coupling Research Articles

Multiphysics simulation of magnetoelectric micro core-shells for wireless cellular stimulation therapy via magnetic temporal interference.

This paper presents an innovative approach to wireless cellular stimulation therapy through the design of a magnetoelectric (ME) microdevice. Traditional electrophysiological stimulation techniques for neural and deep brain stimulation face limitations due to their reliance on electronics, electrode arrays, or the complexity of magnetic induction. In contrast, the proposed ME microdevice offers a self-contained, controllable, battery-free, and electronics-free alternative, holding promise for targeted precise stimulation of biological cells and tissues. The designed microdevice integrates core shell ME materials with remote coils which applies magnetic temporal interference (MTI) signals, leading to the generation of a bipolar local electric stimulation current operating at low frequencies which is suitable for precise stimulation. The nonlinear property of the magnetostrictive core enables the demodulation of remotely applied high-frequency electromagnetic fields, resulting in a localized, tunable, and manipulatable electric potential on the piezoelectric shell surface. This potential, triggers electrical spikes in neural cells, facilitating stimulation. Rigorous computational simulations support this concept, highlighting a significantly high ME coupling factor generation of 550 V/m·Oe. The high ME coupling is primarily attributed to the operation of the device in its mechanical resonance modes. This achievement is the result of a carefully designed core shell structure operating at the MTI resonance frequencies, coupled with an optimal magnetic bias, and predetermined piezo shell thickness. These findings underscore the potential of the engineered ME core shell as a candidate for wireless and minimally invasive cellular stimulation therapy, characterized by high resolution and precision. These results open new avenues for injectable material structures capable of delivering effective cellular stimulation therapy, carrying implications across neuroscience medical devices, and regenerative medicine.

Enhanced dielectric, magnetic and magnetoelectric properties in 0.5BaFe12O19 - xBaTiO3 - (0.5-x)CoFe2O4 composites

(0.5)BaFe12O19 - xBaTiO3 - (0.5-x)CoFe2O4; (x = 0.1, 0.2, 0.3 & 0.4) composite system was developed through conventional solid-state technique. XRD with Rietveld refinement confirmed pure tri-phasic composites with no impurity. The microstructure of samples has inhomogeneous grain packing with average size of grains ∼0.5 μm and typically decreased with BaTiO3 increment. The dielectric constant showed low-frequency dispersion and increased with BaTiO3 increment, hence maximum at 400 °C for composite x = 0.4 (∼2.8 × 103 at 1 kHz). Composites are ferrimagnetic in nature along with presence of firm exchange coupling among BaFe12O19/CoFe2O4 ferrite phases. The samples are multiferroic owing to typically high magnetoelectric coupling coefficient which increased with BaTiO3 increment, thus composite x = 0.4 attains highest value of 4.56 mV/cm.Oe on application of ac magnetic field (Hac = 45 Oe). The results indicate that the composites are suitable for magnetic field sensors and memory storage devices.

High magnetoelectric coupling in piezoelectric modified BNT and magnetic NZFO particulate composite

Lead-free magnetoelectric (ME) particulate composite comprising piezoelectric 72.5Bi0·5Na0·5TiO3-22.5Bi0·5K0·5TiO3–5BiMg0·5Ti0·5O3 (MBNT) and piezomagnetic Ni0·7Zn0·3Fe2O4 (NZFO) in varying phase fraction, i.e., (1-x)MBNT-xNZFO (x = 0.05–0.30; Δx = 0.05) was prepared by solid state reaction route. Their structural, electrical, magnetic and ME properties were investigated. The high temperature sustainability up to 390 °C and the relaxor behavior was confirmed by their dielectric study. The room temperature dielectric constant (∼1081 at 1 kHz), saturation polarization (∼37.12 μC/cm2) and electro-strain (∼0.22 %) was observed maximum for pure MBNT, which decreases in composites with the induction of non-ferroelectric NZFO content. All composites exhibited magnetic hysteresis behavior where net increase in magnetization was associated with the relative increase in NZFO that possessed a saturation magnetization of 74.52 emu/g. At the optimum phase fraction of composite (i.e., 0.80MBNT-0.20NZFO), giant ME coefficient (∼58.12 mV/cm.Oe at 800 Oe) was observed at low frequency of 10 Hz, which suggest its credibility for energy harvester.

Electric field control of magnetization reversal in FeGa/PMN-PT thin films

Abstract Artificial magnetoelectric materials possess huge potential to be utilized in the development of energy efficient spintronic devices. In the past decade, the search for a good ferromagnetic/ferroelectric combination having the ability to create high magnetoelectric coupling, created new insights and also new challenges. In this report, the magnetoelectric effect is studied in the FeGa/PMN-PT(001) multiferroic heterostructures in the presence of electric fields via strain-mediated effects. The formation of magnetic anisotropy in FeGa is observed after changing the polarization of PMN-PT to out-of-plane orientations. The magnetic domain structures forming during the magnetization reversal were studied in compressive, tensile and remanent strained states. The changes in the magnetic properties were reversible after each cycling of the electric field polarity, hence creating a non-volatile system. The control of magnetization switching sustained by an ON–OFF electric field makes our multiferroic heterostructure suitable for application in low-power magnetoelectric based memory applications.

CO2 -Induced Spin-Lattice Coupling for Strong Magnetoelectric Materials.

The preparation of 2D magnetoelectric (ME) nanomaterials with strong ME coupling is crucial for the fast reading and writing processes in the next generation of storage devices. Herein, 2D BaTiO3 (BTO)-CoFe2 O4 (CFO) ME nanocomposites are prepared through a substrate-free coupling strategy using supercritical CO2 . Such 2D BTO-CFO with strong coupling is built through alternating in-plane and out-of-plane epitaxy stacking, leading to remarkable mutual biaxial strain effects for spin-lattice coupling. As a results, such strain effect significantly enhances the ferroelectricity of BTO and the ferrimagnetism of CFO, where an unexceptionally high ME coupling coefficient of (325.8mVcm-1 Oe-1 ) is obtained for the BTO-CFO nanocomposites.

Effect of Hf alloying on magnetic, structural, and magnetostrictive properties in FeCo films for magnetoelectric heterostructure devices

Materials with high magnetoelectric coupling are attractive for use in engineered multiferroic heterostructures with applications such as ultra-low power magnetic sensors, parametric inductors, and non-volatile random-access memory devices. Iron–cobalt alloys exhibit both high magnetostriction and high saturation magnetization that are required for achieving significantly higher magnetoelectric coupling. We report on sputter-deposited (Fe0.5Co0.5)1−xHfx (x = 0 – 0.14) alloy thin films and the beneficial influence of Hafnium alloying on the magnetic and magnetostrictive properties. We found that co-sputtering Hf results in the realization of the peening mechanism that drives film stress from highly tensile to slightly compressive. Scanning electron microscopy and x-ray diffraction along with vibrating sample magnetometry show reduction in coercivity with Hf alloying that is correlated with reduced grain size and low film stress. We demonstrate a crossover from tensile to compressive stress at x ∼ 0.09 while maintaining a high magnetostriction of 50 ppm and a low coercive field of 1.1 Oe. These characteristics appear to be related to the amorphous nature of the film at higher Hf alloying.

Development of a novel lead free (CoFe1.9Bi0.1O4/BaTi0.89Sn0.11O3/CoFe1.9Bi0.1O4) magnetoelectric composite via new design strategy

A novel lead free ceramic based magnetoelectric (ME) tri-layered composite with new design strategy has been fabricated by using sol-gel synthesized Bi3+ doped CoFe2O4 and Sn4+ doped BaTiO3. Structural, microstructural, magnetostriction, piezoelectric and magnetoelectric properties of the synthesized materials and developed system have been thoroughly investigated. CoFe1.9Bi0.1O4 have shown the improvement of magnetostriction (∼259 ppm) and strain sensitivity (∼323 ×10−9 Oe−1) compared to those of un-doped CoFe2O4 (magnetostriction ∼163 ppm and strain sensitivity ∼99 ×10−9 Oe−1). On the other hand, the piezoelectricity of BaTi0.89Sn0.11O3 has improved to 424 pC/N from a value of 194 pC/N for un-doped BaTiO3. The unique design strategy (where the output signal has been collected directly from the piezoelectric layer) and the simultaneous improvement of both the magnetostriction and piezoelectricity of the corresponding components have helped in achieving high ME coupling in the final device. The achievement of high values of in-plane ME coupling coefficients (αME) (α31) at off-resonance and zero-bias resonance conditions (αME ∼49 and 750 mV.cm−1. Oe−1, respectively) have proven the ability of the fabricated device in various potential applications related to magnetic field sensing and magnetoelectric effect.

Solid-State Lithium Ion Supercapacitor for Voltage Control of Skyrmions.

Ionic control of magnetism gives rise to high magnetoelectric coupling efficiencies at low voltages, which is essential for low-power magnetism-based nonconventional computing technologies. However, for on-chip applications, magnetoionic devices typically suffer from slow kinetics, poor cyclability, impractical liquid architectures, or strong ambient effects. As a route to overcoming these problems, we demonstrate a LiPON-based solid-state ionic supercapacitor with a magnetic Pt/Co40Fe40B20/Pt thin-film electrode which enables voltage control of a magnetic skyrmion state. Skyrmion nucleation and annihilation are caused by Li ion accumulation and depletion at the magnetic interface under an applied voltage. The skyrmion density can be controlled through dc applied voltages or through voltage pulses. The skyrmions are nucleated by single 60 μs voltage pulses, and devices are cycled 750000 times without loss of electrical performance. Our results demonstrate a simple and robust approach to ionic control of magnetism in spin-based devices.

Effect of nano-size on magnetostriction of BiFeO3 and exceptional magnetoelectric coupling properties of BiFeO3_P(VDF-TrFE) polymer composite films for magnetic field sensor application

The existence of magnetostriction in bulk BiFeO3 is still a matter of investigation and it is also an issue to investigate the magnetostriction effect in nano BiFeO3. Present work demonstrates the existence of magnetostrictive strain in superparamagnetic (SPM) BiFeO3 nanoparticles at room temperature and the magnetoelectric (ME) coupling properties in composite form with P(VDF-TrFE). Despite few reports on the magnetostriction effect in bulk BiFeO3 evidenced by the indirect method, the direct method (strain gauge) was employed in this work to examine the magnetostriction of SPM BiFeO3. In addition, a high ME coupling coefficient was observed by the lock-in technique for optimized BiFeO3_P(VDF-TrFE) nanocomposite film. These nanocomposite films also exhibit room-temperature multiferroic properties. These results provide aspects of material with immense potential for practical applications in spintronics and magneto-electronics applications. We report a ME sensor using SPM BiFeO3_P(VDF-TrFE) nanocomposite film for detection of ac magnetic field.

Origin of different microwave absorption in multiferroic Bismuth and Gallium Ferrite

Multiferroic Bismuth Ferrite (BFO) is extensively studied for its application as microwave absorption material. However, the microwave property of another well-known multiferroic material, Gallium Ferrite (GFO) having higher magnetoelectric coupling, is not studied yet to the best of our knowledge. In this work, the origin of different microwave absorption observed in BFO and GFO is discussed in detail. A GFO-Resin composite of 6.2 mm length reports a reflection loss of −67.36 dB along with a bandwidth of 5.23 GHz attributed to its good electromagnetic properties and strong impedance matching.

Ionic-triggered magnetoelectric coupling for magnetic sensing applications

The manipulation of electric properties by magnetic fields in magnetoelectric (ME) materials has driven significant research activity and industrial attention, as a result of their disruptive technological potential. Conventional ME nanocomposites exhibit low ME responses, involve electric poling, and AC magnetic excitation after fabrication. Such limitations hinder their full implementation in the scope of the digitalization of society (Internet of Things and Industry 4.0). In this work all those technological/scientific problems are jointly addressed through the nanoengineering of a new type of ME coupling, whose voltage response is ionic-triggered. The polymer-based nanocomposite with 20 weight percentage (wt.%) of [Bmim][Cl] ionic liquid and 30 wt.% of CoFe2O4 leads to the highest ME coupling coefficient reported in the literature (≈ 0.6 V.cm−1.Oe−1), value that is promising for applications, as demonstrated by its incorporation on a speed sensor.

A magnetoelectric nanocomposite based on two dimensional Cr2O3 and CoFe2O4

Nanocomposites consisting of 2 dimensional (2D) amorphous Cr2O3-CoFe2O4 and crystalline 2D Cr2O3-CoFe2O4 were prepared and the room temperature magnetoelectric coupling was studied. This study also investigated the effect of crystalline 2D Cr2O3 on the exchange bias induced magnetoelectric coupling in the composites. Evidence for the exchange bias in the composites is obtained from field cooling - zero field cooling (FC-ZFC) measurements. The 2D crystalline Cr2O3 composite exhibits high magnetoelectric coupling coefficient at room temperature when compared to bulk composite for the corresponding Cr2O3. These composites augurs well for applications especially for energy harvesting and spintronics.

Tutorial: Piezoelectric and magnetoelectric N/MEMS—Materials, devices, and applications

Nano- and micro-electromechanical systems (N/MEMSs) are traditionally based on electrostatic or piezoelectric coupling, which couples electrical and mechanical energy through acoustic resonator structures. Most recently, N/MEMS devices based on magnetoelectrics are gaining much attention. Unlike electrostatic or piezoelectric N/MEMS that rely on an AC electric field or voltage excitation, magnetoelecric N/MEMS rely on the electromechanical resonance of a magnetostrictive/piezoelectric bilayer heterostructure exhibiting a strong strain-mediated magnetoelectric coupling under the excitation of a magnetic field and/or electric field. As a consequence, magnetoelectric N/MEMS enable unprecedented new applications, ranging from magnetoelectric sensors, ultra-compact magnetoelectric antennas, etc. This Tutorial will first outline the fundamental principles of piezoelectric materials, resonator design, specifically different acoustic modes, and piezoelectric-based N/MEMS applications, i.e., radio frequency front end filters and infrared radiation sensors. We will then provide an overview of magnetoelectric materials and N/MEMS focusing on the governing physics of the magnetoelectric effect, magnetic material properties for achieving high magnetoelectric coupling, state-of-the-art magnetoelectric N/MEMS devices, and their respective applications.

Multiferroic Cantilevers Containing a Magnetoactive Elastomer: Magnetoelectric Response to Low-Frequency Magnetic Fields of Triangular and Sinusoidal Waveform.

In this work, multiferroic cantilevers comprise a layer of a magnetoactive elastomer (MAE) and a commercially available piezoelectric polymer-based vibration sensor. The structures are fixed at one end in the horizontal plane and the magnetic field is applied vertically. First, the magnetoelectric (ME) response to uniform, triangle-wave magnetic fields with five different slew rates is investigated experimentally. Time and field dependences of the generated voltage, electric charge, and observed mechanical deflection are obtained and compared for four different thicknesses of the MAE layer. The ME responses to triangular and sinusoidal wave excitations are examined in contrast. Second, the ME response at low frequencies (≤3 Hz) is studied by the standard method of harmonic magnetic field modulation. The highest ME coupling coefficient is observed in the bias magnetic field strength of ≈73 kA/m and it is estimated to be about 3.3 ns/m (ME voltage coefficient ≈ 25 V/A) at theoretically vanishing modulation frequency ( Hz). Presented results demonstrate that the investigated heterostructures are promising for applications as magnetic-field sensors and energy harvesting devices.

Lithium‐Ion Battery Technology for Voltage Control of Perpendicular Magnetization

AbstractThe voltage control of magnetism is a promising path to the development of low‐power spintronic devices. Magneto‐ionics—exploiting voltage‐driven ion migration to control magnetism—has attracted interest because it can generate large magnetoelectric effects at low voltage. Here, the use of the solid‐state lithium‐ion battery technology for reversible voltage‐controlled switching between perpendicular and in‐plane magnetization states in a Co–Pt bilayer is demonstrated. Due to the small size and high mobility of lithium ions, small voltages produce an exceptionally high magnetoelectric coupling efficiency of at least 7700 fJ V–1 m–1 at room temperature. The magnetic switching effect is attributed to the modulation of spin‐orbit coupling at the Co–Pt interface when lithium ions migrate between a lithium storage layer (LiCoO2) and the magnetic interface across a lithium phosphorous oxynitride (LiPON) solid‐state electrolyte, which is corroborated by density functional theory calculations. Voltage control of magnetism in the battery structure does not show degradation over more than 500 voltage cycles, demonstrating promise for solid‐state lithium‐based magneto‐ionic devices.

Al3Fe5O12 nanoparticles loaded electrospun PVDF fibres: An inorganic-organic material with multifunctional traits

In this paper, we report on the development of an organic-inorganic hybrid multiferroic material based on polyvinylidene fluoride (PVDF) and nanostructured aluminium iron garnet (Al3Fe5O12) that is found to exhibit enhanced coupling between ferroelectric and magnetic orderings at room temperature. In addition to the promising multiferroic feature, PVDF-based multiferroics can display a remarkable degree of flexibility, giving increased advantage in device fabrication. With a view of extending the synthesis of the PVDF/Al3Fe5O12 hybrid material to a commercial level, in this work we adopted a simple strategy of electrospinning, and various degrees of Al3Fe5O12 nanoparticles incorporations have been tested to manipulate the strength of the interaction between the two diverse materials. Systematic studies have been conducted to elucidate the arrangement of PVDF chains in the electroactive β-phase configuration. Furthermore, magnetic studies have been conducted in this work to validate the existence of magnetic ordering in the PVDF/Al3Fe5O12 hybrid material systems. A high magnetoelectric coupling coefficient (6.19 mV cm−1 Oe−1) has been noticed for the PVDF/Al3Fe5O12 hybrid material containing 16 wt % Al3Fe5O12 nanoparticles. The evolution of defects with the incorporation of Al3Fe5O12 nanoparticles has been further explored using positron annihilation spectroscopy, which revealed the presence of free volume defects in large concentrations which evolve into Al3Fe5O12 nanoparticles decorated cavities with increased filler loading. The multifunctional nature enables the fabricated PVDF/Al3Fe5O12 hybrids as promising materials for the development of smart devices.

Mechanism of Doping-Induced Orientation of Magnetic Phase in a Sol–Gel-Derived Ni0.5Zn0.5Fe2O4/BaTiO3 Multiferroic Thin Film with High Magnetoelectric Coupling

Mechanism of Doping-Induced Orientation of Magnetic Phase in a Sol–Gel-Derived Ni_0.5Zn_0.5Fe₂O₄/BaTiO₃ Multiferroic Thin Film with High Magnetoelectric Coupling

In situ formation of composite thin film with (111) oriented Ni0.5Zn0.5Fe2O4 pillar array surrounded by BaTiO3 for ferroelectric-ferromagnetic coupling

For a new breakthrough of highly efficient magnetoelectric (ME) coupling of multiferroic composite thin film in application of next generation multifunctional devices, it is important to control constituent magnetic phase pillar array independently embedded inside piezoelectric phase. In this work, in situ spin-coated xNi0.5Zn0.5Fe2O4/(1-x)BaTiO3 composite thin films on Si substrate with high magnetoelectric coupling are successfully obtained via phase separation. Results show that hexagonal Ni0.5Zn0.5Fe2O4 (NZFO) grain grows (111)-oriented as single crystal pillars arrayed independently uniformly and surrounded by BaTiO3 (BTO) phase. Ti and Fe ions are doped into the NZFO and BTO phases respectively and decreased with the decrease in corresponding constituent phases. Grain size and lattice constant of the cubic NZFO are from ~1 to ~0.5 μm and from 0.8383 nm to 0.8369 nm respectively in terms of x. The orientation degree of thin films is> 56% when x is above 0.8. The 0.8NZFO/0.2BTO thin film with and without pure BTO after-spincoated shows giant ME coupling effect, about 40% change of magnetization of NZFO in terms of phase transition of ferroelectric BTO at Curie temperature ~398 K. It is much larger than others on Si substrate ever reported and may be applied cost-effectively, coupling-efficiently and widely in Si-based chips area.

Dielectric and magnetoelectric coupling properties of Lead-free (1-x) Bi 0.9Sm 0.1FeO 3/ (x) La 0.7Sr 0.3MnO3 (x = 0, 0.05, 0.1) composites at room temperature

Multiferroic composites (1-x) Bi 0.9Sm 0.1FeO 3/ (x) La 0.7Sr 0.3MnO3 (x = 0, 0.05, 0.1) have been synthesized and their dielectric and magnetoelectric (ME) properties were measured at room temperature. X-ray diffraction patterns show peaks corresponding to both Bi 0.9Sm 0.1FeO 3 (BSFO) and La 0.7Sr 0.3MnO3 (LSMO) phase, which indicates the successful formation of composites. The frequency responses of dielectric properties have been investigated over a wide range of frequencies at room temperature. The dielectric constant and AC conductivity of the samples enhances with increasing content of LSMO. Furthermore, the ME responses of the samples were analyzed at room temperature shows highest ME coupling value of 24.67 mV/cm Oe for composite with x = 0.05. It could generate up to 2.05 V/cm for a magnetic field of 86 Oe. The voltage generation in the composite with modulating AC field maintains a linear relation and point towards the direct application of the material in a variety of next generation low power consuming devices working at room temperature.

Single crystal growth and structural, magnetic, and magnetoelectric properties in spin-frustrated bow-tie lattice of α-Cu5O2(SeO3)2Cl2

Growth of α-Cu5O2(SeO3)2Cl2 single crystals with unique up-up and down-down ferromagnetic spin-dimers that results in higher magnetoelectric coupling.