Coefficient αME Research Articles

Enhanced magnetoelectric response in Sc-doped BiFeO3-BaTiO3 Ceramics

In recent years, the single-phase BiFeO3-BaTiO3 multiferroic ceramics have gained attention for their magnetoelectric response above room temperature, but substantial endeavors to improve the property have yielded modest results. An optimized BiFe(1-x)ScxO3-BaTiO3 composition having magnetoelectric coefficient (αME) ∼ 567 mV/(cm·Oe)) measured at the resonant frequency (∼95 kHz) is reported in this work. The high αME is attributed to the combined effect of improved piezoelectric coefficient and enhanced ferromagnetism. Improved piezoelectricity is attributed to enhanced intrinsic response caused by the octahedral distortions, and enhanced ferromagnetism is induced by the destabilized cycloidal spin structure resulting from the octahedral distortions. Besides, the addition of Sc3+ can exhibit increased resistivity and reduced defect dipole effects, which is conducive to improving electric properties.

Settlement stability, electrical properties, and magnetoelectric properties of Mn0.5Zn0.5Fe2O4-PbZr0.5Ti0.5O3 multiferroic fluids modulating by particle sizes

Mn0.5Zn0.5Fe2O4-PbZr0.5Ti0.5O3 (MZFO-PZT) multiferroic fluids with different MZFO particle sizes were prepared, and magnetoelectric coupling effects were observed to be enhanced at room temperature. The X-ray diffraction analysis (XRD) indicates that the MZFO and PZT particles are in the pure phases. Scanning electron microscopy (SEM) images illustrate a decrease in MZFO particle size with increased ball milling time. As the MZFO particle sizes decrease, the settlement stability of multiferroic fluids becomes worse. The dielectric constant displays a nonlinear variation, exhibiting a maximum value of 4.52 at 140 Hz when the MZFO particle size is 0.55 μm. The residual polarization strength decreases and increases as particle size decreases, while the saturation polarization strength decreases gradually. The application of magnetic field results in a notable enhancement of the dielectric characteristics and ferroelectric properties, which indicates the presence of magnetodielectric and magnetoelectric coupling effects. The magnetoelectric coupling coefficient (αME) is 15.14 V/(cm·Oe) when the MZFO particle size is 0.61 μm. By modifying the strength of the applied magnetic field, the αME attains a maximum value of 114.43 V/(cm·Oe). This approach offers an effective strategy for optimizing the magnetoelectric coupling effect of multiferroic materials. Therefore, it is expected to be used in new magnetoelectric devices such as magnetoelectric random memories and magnetic field sensors.

Simultaneously enhanced ferroelectric and magnetic properties of SrTiO3‐modified Bi0.88Sm0.12FeO3 ceramics

AbstractIn the present study, SrTiO3 was selected to enhance the multiferroic characteristics of Bi0.88Sm0.12FeO3 (BSF) ceramics. With increasing SrTiO3 content, the principal phase of BSF ceramic transitions from rhombohedral R3c to Pna21. Through DSC and dielectric analysis, it was observed that both the Curie temperature and Néel temperature decreased proportionally with the augmentation of SrTiO3 content. When x = .1, the optimal ferroelectric performance is achieved, and the highest remanent polarization value is 55.47 µC/cm2, significantly surpassing that of BSF ceramics. Moreover, the PFM test results showed that as the substitution content increased, the domains in the BSF ceramic gradually transformed from normal ferroelectric domains to polar nanomicro‐domains. Magnetic and magnetoelectric results show that when x = .1, the best magnetic properties are obtained, Mr = 59.7 emu/mol. The magnetoelectric coefficient αME initially increased and then decreased with the increasing SrTiO3 content, reaching its optimum magnetoelectric properties at x = .1, where αME = .47 mV cm–1 Oe–1. In summary, when the substitution amount of SrTiO3 reaches 10%, the ferroelectric, magnetic, and magnetoelectric properties of BSF ceramics are significantly improved.

Direct and converse piezoelectricity of thickness tuned BCZT ceramics: toward efficient bilayered magnetoelectric devices

Here we report the effect of thickness reduction of bulk 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Ti0.8Zr0.2)O3 (BCZT) pellet on its direct and indirect piezoelectric properties. Upon reducing the thickness to 0.3 mm, the pellet shows a very high electrostrain of ∼0.7% and piezoelectric coefficient of ∼353 pC/N which were ∼0.14% and 258 pC/N for the 1 mm thick sample. These results have been correlated with the reduction in hardness and mutual mechanical clamping between the grains due to the reduced thickness of BCZT. Due to this improved strain sensitivity, the bilayered magnetoelectric (ME) devices of BCZT with magnetostrictive CoFe1.9Bi0.1O4 (CFBO) pellet have also shown gradually improved ME coupling coefficient ( αME ) with reduced BCZT thickness ( αME = 27 and 66 mV·cm−1·Oe−1 for 1 and 0.3 mm BCZT thickness, respectively). This demonstrates the possible applicability of thickness tuned BCZT pellets for various technological purposes.

A Spin-Charge-Regulated Self-Powered Nanogenerator for Simultaneous Pyro-Magneto-Electric Energy Harvesting.

In view of the depletion of natural energy resources, harvesting energy from waste is a revolution to simultaneously capture, unite, and recycle various types of waste energies in flexible devices. Thus, in this work, a spin-charge-regulated pyro-magneto-electric nanogenerator is devised at a well-known ferroelectric P(VDF-TrFE) copolymer. It promptly stores thermal-magnetic energies in a "capacitor" that generates electricity at room temperature. The ferroelectric domains are regulated to slip at the interfaces (also twins) of duly promoting polarization and other properties. An excellent pyroelectric coefficient p ∼ 615 nC·m-2·K-1 is obtained, with duly enhanced stimuli of a thermal sensitivity ∼1.05 V·K-1, a magnetoelectric coefficient αme ∼8.8 mV·cm-1·Oe-1 at 180 Hz (resonance frequency), and a magnetosensitivity ∼473 V/T. It is noteworthy that a strategy of further improving p (up to 41.2 μC·m-2·K-1) and αme (up to 23.6 mV·cm-1·Oe-1) is realized in the electrically poled dipoles. In a model hybrid structure, the spins lead to switch up the electric dipoles parallel at the polymer chains in a cohesive charged layer. It is an innovative approach for efficiently scavenging waste energies from electric vehicles, homes, and industries, where abundant thermal and magnetic energies are accessible. This sustainable strategy could be useful in next-generation self-powered electronics.

Magnetoelectric, dielectric, and magnetic investigations of multiferroic NixCo1−xFe2O4−SryBa1−yNb2O6 composites

Magnetoelectric (NixCo1−xFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites with a 0–3 connectivity and different cation stoichiometries were synthesized via a classical mixed-oxide method. XRD patterns of all ceramics show reflections of the target phases SryBa1−yNb2O6 and NixCo1−xFe2O4. The influence of stoichiometry of the ferrimagnetic and ferroelectric phase on the magnetoelectric behavior was studied on composites with composition of (NixCo1−xFe2O4)0.3−(Sr0.5Ba0.5Nb2O6)0.7 and (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7. The magnetic Curie temperature increases with nickel content. However, the saturation magnetizations as well as the Curie temperatures of the composites are always lower than the ones of bulk NixCo1−xFe2O4 samples. The maximum magnetoelectric coefficient (αME) rises with increasing nickel content from 40 (x = 0) to 180 µV Oe−1 cm−1 (x = 1) in accordance with the dynamic magnetostriction coefficient. The evolution of αME of (NiFe2O4)0.3−(SryBa1−yNb2O6)0.7 composites shows an increase with strontium content up to y 0.5. Higher strontium content leads to a significant reducing of αME.

Evidence of self-biased magnetoelectric coupling in eco-friendly (Na0.41K0.09Bi0.5TiO3-Ba0.85Ca0.15Zr0.1Ti0.9O3)-(CoFe2O4) particulate composites

The magnetoelectric (ME) properties of eco-friendly 1-x(0.94Na0.41K0.09Bi0.5TiO3-0.06Ba0.85Ca0.15Zr0.1Ti0.9O3)-x (CoFe2O4) (NKBCZT-CFO) with x = 0, 0.1, 0.2, 0.3 and 0.4 particulate composites were investigated. The X-ray diffraction studies provided evidence for the simultaneous existence of constituent phases (ferroelectric and ferromagnetic) in the composite. The structural and surface morphology analysis of the composite affirmed the homogeneous and densely packed distribution of CFO grains within the NKBCZT matrix. The composite's multiferroic behavior at room temperature was confirmed through the characterization of P vs E and M vs H hysteresis loops. The observed values of remnant polarization (Pr) and coercive field (Ec) are 26.7 μC/cm2 and 35.5 kV/cm, respectively, for 10 mol% of CFO. The increase in CFO content resulted in a decrease in the ferroelectric properties, possibly due to the conductive behaviour exhibited by CFO, and correlated with leakage current measurement. For the composite containing 40 mol% of CFO, the estimated values of remanent (Mr), saturation (Ms) magnetization, coercive field (Hc), and magnetic moment (µB) are 2.35 emu/g, 21.85 emu/g, 104.2 Oe, and 0.86 µB, respectively. The non-Debye type dielectric relaxation processes have been observed in the composites, and the electron hopping mechanism resulted in a higher dielectric constant (εʹ). Enhancement in relaxor nature had been observed through Vogel-Fulcher analysis with CFO content. The evidence of ME coupling was revealed through the direct ME voltage coefficient (αME) and magnetocapacitance (MC) measurement. The observed maximum value of MC measured at 1 kHz for the 20 mol% CFO is ∼5.6 %. Self-biased ME coupling (non-zero αME at HDC = 0 Oe) was observed in 20 and 30 mol% of CFO composite. The highest measured value of αME for 20 and 30 mol% CFO is 3.63 mV/cm.Oe and 4.09 mV/cm.Oe at HDC = 0 Oe respectively. The strong ME interaction and significant value of self-biased ME αME suggest that these composites can be explored for magnetic sensor and ME memory device applications.

Improvement of the magnetoelectric response in NiFe2O4−Sr0.5Ba0.5Nb2O6 composites using LiNbO3 as sintering additive

Magnetoelectric (NiFe2O4)0.3−(Sr0.5Ba0.5Nb2O6)0.7 composites with addition of LiNbO3 as sintering additive were prepared by a classical mixed-oxide method. XRD patterns of ceramics sintered between 1000 and 1200 °C show the desired Sr0.5Ba0.5Nb2O6 and NiFe2O4 phases. SEM investigations confirm the 0–3 connectivity of the composite ceramics. The addition of 10 and 20 mol% LiNbO3 improves the densification of the composite ceramics and leads to an increase of the size of the Sr0.5Ba0.5Nb2O6 grains. Magnetic measurements show hystereses with low coercivities. Dielectric measurements were carried out depending on temperature and frequency. The samples with the LiNbO3 addition show significantly higher resistivity values (σDC). Magnetoelectric measurements were carried out in dependence of the magnetic DC-field, temperature, and frequency. The maximum magnetoelectric coefficient (αME) rises with the addition of LiNbO3 from 180 to 803 µV Oe−1 cm−1 (@900 Hz). Temperature dependent measurements show a continuously decreasing of αME with lower temperature.

Enhanced ferroelectric and magnetic properties of the 0–3 type BiFeO3-BaTiO3/BaFe12O19 composite multiferroic material

The 0–3 type (1-x)(0.75BiFeO3-0.25BaTiO3)/xBaFe12O19 (BFO-BTO/BaM) multiferroic composites were successfully prepared by a solid-state reaction sintering process. The coexistence of perovskite BFO-BTO phase and hexagonal BaM phase was confirmed for all BFO-BTO/BaM composites. Due to the large leakage current, the breakdown electric field decreased with increasing BaM content. Nevertheless, the ferroelectric properties of the composite ceramics have also been significantly improved, mainly as the increase of remanent polarization and the decrease of coercive field, where Pr = 19.79 μC/cm2, Ec = 30 kV/cm at x = 0.075. Meanwhile, the magnetic properties of BFO-BTO phase were enhanced, and the remanent magnetization linearly increased with increasing BaM content. The single domain magnetic structure was obtained for all BFO-BTO/BaM composite ceramics, and the magnetic properties changed after electric poling, which indicated the electric field controlled magnetic properties. The electric-controlled magnetic behavior was attributed to the structural phase transition. The magnetoelectric coupling coefficient αME of the composite material has been improved, with a maximum value of 0.61 mV/cm.Oe. Thus, the BFO-BTO/BaM magneto-electric composite system is a promising multiferroic system in information technology and sensing fields.

Magnetoelectric nanoparticles shape modulates their electrical output.

Core-shell magnetoelectric nanoparticles (MENPs) have recently gained popularity thanks to their capability in inducing a local electric polarization upon an applied magnetic field and vice versa. This work estimates the magnetoelectrical behavior, in terms of magnetoelectric coupling coefficient (αME), via finite element analysis of MENPs with different shapes under either static (DC bias) and time-variant (AC bias) external magnetic fields. With this approach, the dependence of the magnetoelectrical performance on the MENPs geometrical features can be directly derived. Results show that MENPs with a more elongated morphology exhibits a superior αME if compared with spherical nanoparticles of similar volume, under both stimulation conditions analyzed. This response is due to the presence of a larger surface area at the interface between the magnetostrictive core and piezoelectric shell, and to the MENP geometrical orientation along the direction of the magnetic field. These findings pave a new way for the design of novel high-aspect ratio magnetic nanostructures with an improved magnetoelectric behaviour.

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.

Functionality Tuning in Hierarchically Engineered Magnetoelectric Nanocomposites for Energy-Harvesting Applications.

The β-phase of the copolymer poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) possesses the highest dipole moment among all the functional polymers. It remains a key component of flexible energy-harvesting devices based on piezoelectricity and triboelectricity in the last decade. However, the quest for P(VDF-TrFE)-based magnetoelectric (ME) nanocomposites with enhanced ferroelectric, piezoelectric, and triboelectric properties remains elusive. The magnetostrictive inclusion in the copolymer matrix forms electrically conducting pathways and degrades β-phase crystallinity significantly, deteriorating the functional properties of the nanocomposite films. To address this issue, we report the synthesis of magnetite (Fe3O4) nanoparticles on micron-scale magnesium hydroxide [Mg(OH)2] templates. These hierarchical structures were incorporated within the P(VDF-TrFE) matrix rendering composites with enhanced energy-harvesting capability. The Mg(OH)2 template prevents the formation of a continuous network of magnetic fillers, leading to lower electrical leakage in the composite. The addition of dual-phase fillers with 5 wt % only increases remanent polarization (Pr) values by ∼44%, owing to the presence of the β-phase with significant crystallinity and increased interfacial polarization. The composite film exhibits a quasi-superparamagnetic nature and a significant magnetoelectric coupling coefficient (αME) of 30 mV/cm Oe. The film was also employed for triboelectric nanogenerator applications, exhibiting five times higher power density than the pristine film. We finally explored the integration of our ME devices with an internet of things platform to monitor the operational status of electrical appliances remotely. In light of these findings, the present work opens the path for future self-powered, multifunctional, and flexible ME devices with new application domains.

Enhanced magnetoelectric coupling in novel rare earth metal substituted Sr based Z-hexaferrites/P(VDF-HFP) composites

This research is driven by a desire to create composite films that combine the ferrimagnetic capabilities of pure and La/Nd substituted Sr3Co2Fe24O41 Z-hexaferrites with the multifunctional features of ferroelectric polymers. A flexible magnetoelectric (ME) polymer composite films, with Sr3Co2Fe24O41 (SF), Sr2.85La0.15Co2Fe24O41(SF–La) and Sr2.85Nd0.15Co2Fe24O41 (SF-Nd) as the ferrimagnetic material and poly vinylidene fluoride-hexafluoropropylene (PH) as a ferroelectric component, were synthesized using solution casting method. In the current case, two steps have been used to synthesize ferroelectric and ferrimagnetic composites films: first, SF, SF-La and SF-Nd hexaferrite samples were synthesized using solid state reaction method and then 20% weight percentage of these hexaferrites were incorporated into the PH matrix using solution casting method to form composite film. In order to find the traces of collaborative interactions between the two phases, the structural, magnetic, and ferroelectric properties of these composite samples have been studied. The XRD data confirm the formation of SF, SF-La and SF-Nd hexaferrite dispersed in a piezoelectric copolymer PH matrix. The changes in the ferroelectric properties in different magnetic fields demonstrated the existence of ME coupling in the composite films. The inclusion of PH enhanced the magnetoelectric coupling of composite films. The maximal value of magnetoelectric coupling coefficient (αME) observed is 0.213, 1.227, 3.403 and 9.797 mV cm−1 Oe−1 for SF, PHSF, PHSF-La and PHSF-Nd, respectively. There is approximately 46-time increase in the maximum value of magnetoelectric coupling coefficient (αME) in PHSF-Nd (9.797 mV/cm.Oe) composites as compare to pure SF (0.213 mV/cm.Oe).

Development of Lead Free Magnetoelectric Materials for Magnetic Field Sensor applications

(100-x) Na0.5Bi0.5TiO3 (NBT)-(x) NiFe2O4 (NFO)(x = 0, 20, 40, 60, 80 and 100) composites are synthesized using conventional solid state reaction method. Crystal structure studies are performed by using X-ray Diffraction technique (XRD) and the Rietveld analysis of XRD patterns confirms the co-existence of cubic (NFO) and rhombohedral (NBT) symmetry with Fd- 3m and R3c space groups, respectively. Micro-structural study reveals the formation of combination of composite phases and its inter-coupling grains. The average grain sizes and area percentage of each phase for the composites are calculated using Image J software. The Magnetisation versus Magnetic field (M-H) hysteresis loops show soft magnetic behavior of composites with variation in Saturation magnetization (MS) and Coercivity (HC). A maximum MS (34 emu/g) and low HC (15 Oe) is obtained for (80) NFO - (20) NBT composite.The Polarization – Electric field (P-E) analysis shows that the maximum saturation polarization (PS) is obtained for (60)NBT-(40)NFO sample and is attributed to the leakage current generated by conductive NFO phase. The coupling between the ferrite and ferroelectric phase is studied based on the magnetoelectric voltage coefficient(αME). The maximum (αME) of 1.82 mV/cm-Oe is obtained for (80)NBT -(20)NFO sample and this is almost 80% higher than the previously published literature on NBT-NFO composites. This can be attributed to the uniform distribution of grains with each ferroelectric phase surrounded by ferrite phase as shown in the morphological study.

Transition-Layer Implantation for Improving Magnetoelectric Response in Co-fired Laminated Composite

Magnetoelectric (ME) laminated composites with strong ME coupling are becoming increasingly prevalent in the electron device field. In this paper, an enhancement of the ME coupling effect via transition-layer implantation for co-fired lead-free laminated composite (80Bi0.5Na0.5TiO3-20Bi0.5K0.5TiO3)/(Ni0.8Zn0.2)Fe2O4 (BNKT/NZFO) was demonstrated. A transition layer composed of particulate ME composite 0.5BNKT-0.5NZFO was introduced between the BNKT piezoelectric layer and the NZFO magnetostrictive layer, effectively connecting the two-phase interface and strengthening interface stress transfer. In particular, an optimal ME voltage coefficients (αME) of 144 mV/(cm·Oe) at 1 kHz and 1.05 V/(cm·Oe) at the resonant frequency in the composite was achieved, with a layer thickness ratio (BNKT:0.5BNKT-0.5NZFO:NZFO) of 3:1:6. The static elastic model was used to determine strong interface coupling. A large magnetodielectric (MD) response of 3.95% was found under a magnetic field excitation of 4 kOe. These results demonstrate that transition-layer implantation provides a new path to enhance the ME response in co-fired laminated composite, which can play an important role in developing magnetic field-tuned electronic devices.

Magneto-Mechano-Electric generator of lead-free piezoelectric Ba0.95Ca0.05Ti0.95Zr0.025Sn0.025O3 / Co0.8Ni0.2Fe2O4 magnetostrictive multiferroic laminate structure

We report the magneto-mechano-electric (MME) response of (2–2) layered magnetostrictive-piezoelectric composite structures of Co0.8Ni0.2Fe2O4 / Ba0.95Ca0.05Ti0.95Zr0.025Sn0.025O3 / Co0.8Ni0.2Fe2O4 (CNFO/BCTZS/CNFO) ceramics. The basic magnetic and electric properties to support the multiferroism nature were studied and discussed. The BCTZS piezoceramics showed a piezoelectric charge coefficient of (d33) ∼ 149 pC/N, piezoelectric voltage coefficient of (g33) ∼ 7.64 × 10-3 (Vm/N) and planar electromechanical coupling factor of (kp) ∼ 26 % with additional benefits of phase coexistence of orthorhombic-tetragonal lattice symmetries near room temperature. The CNFO magnetostrictive phase reveals a piezomagnetic coefficient (q11 = dλ11/dH) of − 0.0625 ppm/Oe at a lower magnetic field bias of 600 Oe. The MME response of CNFO/BCTZS/CNFO multiferroics is validated by measuring the magnetoelectric (ME) coefficient αME in longitudinal–transverse (L-T) mode. The CNFO/BCTZS/CNFO structure revealed the αME of 50.8 mV/cm·Oe at a field of 644 Oe at off-resonance frequency i.e. 1 kHz. The frequency-dependent αME measurements at two different constants (Hdc), i.e. 100 Oe and 600 Oe showed the resonant enhancement in ME coupling at 8.5 kHz by attaining the peak value of magnetoelectric coefficient αME ∼ 0.27 V/cm·Oe and 0.107 V/cm·Oe respectively. Consequently, it is confirmed that due to the electromechanical resonance effect, the magnitude of αME is increased by six times as that measured at off-resonance i.e. 1 kHz. Therefore, the present multiferroic 2–2 structures are suitable for magneto-mechano-electric (MME) energy harvesters as well as magnetic field sensor applications.

Modeling of core-shell magneto-electric nanoparticles for biomedical applications: Effect of composition, dimension, and magnetic field features on magnetoelectric response.

The recent development of core-shell nanoparticles which combine strain coupled magnetostrictive and piezoelectric phases, has attracted a lot of attention due to their ability to yield strong magnetoelectric effect even at room temperature, thus making them a promising tool to enable biomedical applications. To fully exploit their potentialities and to adapt their use to in vivo applications, this study analyzes, through a numerical approach, their magnetoelectric behavior, shortly quantified by the magnetoelectric coupling coefficient (αME), thus providing an important milestone for the characterization of the magnetoelectric effect at the nanoscale. In view of recent evidence showing that αME is strongly affected by both the applied magnetic field DC bias and AC frequency, this study implements a nonlinear model, based on magnetic hysteresis, to describe the responses of two different core-shell nanoparticles to various magnetic field excitation stimuli. The proposed model is also used to evaluate to which extent realistic variables such as core diameter and shell thickness affect the electric output. Results prove that αME of 80 nm cobalt ferrite-barium titanate (CFO-BTO) nanoparticles with a 60:40 ratio is equal to about 0.28 V/cm∙Oe corresponding to electric fields up to about 1000 V/cm when a strong DC bias is applied. However, the same electric output can be obtained even in absence of DC field with very low AC fields, by exploiting the hysteretic characteristics of the same composites. The analysis of core and shell dimension is as such to indicate that, to maximize αME, larger core diameter and thinner shell nanoparticles should be preferred. These results, taken together, suggest that it is possible to tune magnetoelectric nanoparticles electric responses by controlling their composition and their size, thus opening the opportunity to adapt their structure on the specific application to pursue.

Robust room‐temperature ferroelectricity and magnetoelectric coupling effect in epitaxial CaTiO3/SmFeO3 thin films

AbstractSmFeO3 has received the increasing scientific attention as a promising room‐temperature single‐phase multiferroic material with great application potential in the next‐generation spintronic devices. However, the ferroelectricity of SmFeO3 has remained as a controversial issue. In the present work, high resistivity incipient ferroelectric CaTiO3 was introduced as a charge blocking layer on an SmFeO3 thin film to suppress the leakage current. CaTiO3/SmFeO3/Nb–SrTiO3 (1 0 0) thin films were prepared by a PLD (pulsed laser deposition) process, and the epitaxial growth of thin films was confirmed by XRD (X‐ray diffraction) and HRTEM (high resolution transmission electron microscope) images. The interface strain resulted in the polar non‐centrosymmetry in space group P42/mc for SmFeO3, and subsequently the room‐temperature ferroelectricity was achieved with a robust remanent polarization of about 4.9 μC/cm2. The 180° switchable domain structure was confirmed by PFM (piezoelectric force microscope). Meanwhile, strong magnetoelectric coupling with magnetoelectric coefficient (αME) of about 2.5 V/(cm Oe) was observed. The present work has revealed the structural origin of ferroelectricity in an SmFeO3 thin film and provided the great reference for its room temperature multiferroic applications.

BaTiO3/(Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4)x composites: Analysis of the effect of Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4 doping at different concentrations on the structural, morphological, optical, magnetic, and magnetoelectric coupling properties of BaTiO3

In the present study, composite samples of BaTiO3/(Co0.8Ni0.1Mn0.1Fe1.9Ce0.1O4)x (noted as BTO/(CNMFCO)x) were prepared and their structural, morphological, optical, magnetic, and magnetoelectric coupling properties were investigated. Firstly, the BaTiO3 and spinel ferrite CNMFCO phases were prepared separately through the sol-gel auto-combustion route, then, the composite samples BTO/(CNMFCO)x were made via the solid-state reaction method. The structural, morphological, optical, magnetic, and magnetoelectric coupling properties were examined using X-rays diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), scanning electron microscope (SEM) coupled with EDX spectrometer, UV–visible diffuse reflectance spectrophotometer (UV–vis DRS), vibrating sample magnetometer (VSM) techniques, and lock-in amplifier, respectively. The successful preparation of biphasic samples was confirmed by XRD and SEM studies. From SEM images, a compact structure with good density was observed. The mean size of BTO grains decreases with increasing the concentration of the magnetic phase. The optical properties have been explored in the UV–visible light range. The extracted band gap energy (Eg) values showed a reduction with the rising of the magnetic phase content. The analysis of magnetization measurements revealed the magnetic character of different composites. It is found that the saturation (Ms) and remanent (Mr) magnetizations are increasing with the rise in the concentration of the magnetic CNMFCO phase (x %). High magnetoelectric voltage coefficients (αME) were attained for different composites with the highest αME value of about 22.8 mV/cm.Oe reached in composite with x content of 20%. The high ME coupling in these composites makes these composites promising candidates to be used in multifunctional devices.

Self-biased characteristics of NZCF/BCZT layered magnetoelectric composites: A novel coupling paradigm in magnetoelectricity

Here, we investigate room temperature magnetoelectric (ME) behavior of ferroelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and ferrimagnetic Ni0.75Zn0.20Co0.05Fe2O4 (NZCF) layered composites. The ferroelectric ceramics (thickness, t, ∼0.6, 0.8, and 1.0 mm) are stacked at magnetic specimen of fixed t ∼ 1 mm, coupled with conducting silver epoxy. The phase formation, surface morphology, dielectric, magnetic, magnetoelectric and magnetodielectric characteristics of bilayer composites have been studied in the present work. The maximum value of magnetoelectric (ME) coupling coefficient (αME) is found to be 70, 90, and 110 mVcm−1Oe−1 for composite having ferroelectric layer thickness t ∼ 1, 0.8, and 0.6 mm, respectively. More importantly, αME(H→0) remains finite for composite (t ∼ 0.8, and 0.6 mm) in zero magnetic field, which is a clear evidence of self-biasing phenomenon in NZCF/BCZT layered composite. For closer insight about underlying mechanism, we estimate magnetodielectric (MD) coefficient for the layered composite. The MD coefficient is found to be significantly high ∼6.32% for the thickness 0.6 mm. MD% vs magnetic field, H, curves exhibit steeper field dependence in low field region and for H≥2kOe MD possess saturation characteristics. The high saturation characteristics suggest that the magnetoelectricity in layered composite is driven by magnetostriction mechanism and causes robust ME coupling. Further, we obtain electrical signal ∼143 mV with the Hdc ∼250 Oe, as a consequence of interplaying nature of magneto(striction)- piezo(electricity). Such a sizeable response will improve the underlying intimacy between technology and practical application. The study reveals that the pellet based layered composites may be a proven strategy for the realization of self-biased ME devices.