Fe3O4 Layer Research Articles

Heterostructure Fe2O3/BiVO4 as a Photoanode for a Visible-Light-Responsive Photocatalytic Fuel Cell

Searching earth-abundant materials for photocatalytic fuel cells (PFCs) remains an important goal for energy conversion and storage, and the construction of semiconductor composite materials is an effective method to improve the photochemical properties of photoelectrodes in PFCs. Herein, a simple hydrothermal method is used to load an Fe2O3 layer on a BiVO4 film for use in the photoanode of a PFC, and the electrochemical results show that the short-circuit current density (Jsc) and the open-circuit voltage (Voc) of the PFC reach 3.05 mA/cm2 and 0.84 V under simulated solar irradiation, respectively. Furthermore, a detailed analysis of the density of states, charge density difference, and work functions of the Fe2O3/BiVO4 heterojunction is discussed by the density functional theory (DFT) method, showing the proper band alignment and the existence of a built-in electric field at the interface with the direction from BiVO4 to Fe2O3, which greatly improves the performance of the PFC. This research provides a clear mechanism for the Fe2O3/BiVO4 heterojunction in the PFC system.

Characterization of surface decarburization and oxidation behavior of Cr–Mo cold heading steel

Abstract Herein, the surface decarburization and oxidation characteristics of Cr–Mo cold heading steel are investigated via optical microscopy, scanning electron microscopy, and electron backscatter diffraction under different temperatures. Furthermore, the competitive mechanisms of decarburization and oxidation are analyzed. The results indicate that the heating temperature considerably affects the decarburization and oxidation characteristics of the steel sample. With an increase in the temperature, the depth of the total decarburization layer increases. The fully decarburized layer is prominent between 750 and 850°C and culminates at 800°C. The oxide thickness parabolically increases, and Cr2O3 is present, which inhibits oxidation. Between 700 and 950°C, the oxidation weight gain is slow. The main structure of the oxide scale is the dense Fe3O4 layer, inhibiting decarburization. The oxidation rate increases at 950°C, and the proportion of loose FeO layer in the oxide scale exceeds 66%, promoting decarburization. At >1,000°C, the surface decarburization and oxidation rate simultaneously increase.

In-situ proton irradiation/lead-bismuth eutectic corrosion synergistic effect on corrosion behaviour of 11Cr1W1Si ferritic/martensitic steel

In-situ proton irradiation/lead-bismuth eutectic corrosion synergistic effect on corrosion behaviour of 11Cr1W1Si ferritic/martensitic steel was investigated. The result indicated that irradiation did not change the duplex structure of oxide layer composed of an outer Fe3O4 layer and an inner Fe-Cr spinel layer. However, irradiation-induced damage can accelerate the lead-bismuth eutectic corrosion rate of this steel, and the underlying role of irradiation damage on the corrosion process was considered.

Fractional-unit-cell-doped spinel/perovskite oxide interfaces with switchable carrier conduction

The two-dimensional hole gas (2DHG) at the polar LaAlO3/SrTiO3 interface remains elusive. Different from isostructural perovskite-type interfaces, the spinel/perovskite heterointerface of γ-Al2O3/SrTiO3 (GAO/STO) enables us to control interfacial states with sub-unit-cell precision. Herein, we present the epitaxial growth of fractionally doped GAO/STO heterointerfaces, where GAO is precisely doped on the scale of 1/4-unit-cell (0.2 nm) by ferromagnetic Fe3O4 and nonmagnetic ZnO atomic layers. Notably, the conduction of the engineered interfaces depends critically on the position of the dopant, where a coexistence of electron and hole conduction is measured at even sublayer-doped GAO/STO interfaces. First-principles density functional theory calculations indicate that electron conductivity is from the interfacial TiO2 layers of the STO substrate, while the hole conductivity is from the Zn-doped GAO film. The presence of hole conduction can be explained from the alternating structural feature of a doped layer without oxygen vacancies. This work sheds additional insight on the emergence of 2DHG at oxide interfaces and provides opportunities for atomically engineered oxide interfaces with non-isostructural layers.

Simulation study to improve the sensitivity of surface plasmon resonance sensor by using ferric oxide, nickel and antimonene nanomaterials

In the present paper, a simulation work has been done to study about a hypersensitive Surface Plasmon Resonance (SPR) based sensor device created by the angular interrogation method based on Attenuated Total Reflection (ATR) phenomenon. The numerical analysis has been done by the method of transfer matrix and a plane polarised source of light of wavelength 633 nm approx (632.8 nm wavelength of He-Ne laser) has been used. In this device configuration, glass prism of Calcium fluoride (CaF2) has been used with Silver (Ag) metal using Kretschmann configuration, a diamagnetic material nanosheets of ferric oxide (Fe2O3), nickel (Ni) and a 2D material antimonene is used as a polymeric structure. All the important performing parameters of SPR sensor such as sensitivity, detection accuracy, quality factor has been calculated for different device configuration of SPR sensor. Fe2O3 and Ag layer thickness has been optimized by using genetic algorithms to obtain the highest sensitivity. The configuration gives the highest sensitivity 310°RIU−1 of projected SPR sensor when sensing medium RI varies from 1.330 to 1.335. For proposed design of SPR sensor the sensitivity and FWHM are high as compared to the conventional SPR senor having FWHM value 3.4995 (deg.). For the proposed device configuration bilayer of Ni and antimonene has been used as a polymeric substance to improve the sensitivity and protect device from corrosion. Penetration depth value of 110.5 nm and 3D plot of transverse electric (TM) field intensity has also been plotted. The numerical simulation is based on transfer matrix method and Fresnel equations and the used softwares are MATLAB and COMSOL multiphysics software. The proposed SPR sensor helps to detect the liquid analytes in the field of biomedical and environmental application.

Effect of high-temperature on oxidation behavior of 300 M steel

The isothermal oxidation experiment was utilized on 300 M steel to investigate the oxidation kinetics, morphology characterization, and the formation mechanism of the oxide scale. The cross-sectional morphologies, elements distribution, and phase composition of the oxide scale in 300 M steel were analyzed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) techniques. The results revealed that there are three layers formed consisting of the outer layer, hematite (Fe2O3), the intermediate layer, magnetite (Fe3O4), and the inner layer, wustite (FeO) after the oxidation of 300 M steel at elevated temperature. The oxide scale thickness of 300 M steel increased by increasing the oxidation temperature and time. Meanwhile, the columnar void in the Fe3O4 layer grew wider and gradually extended until it transformed into large cavity. The interface between the oxide scale and the steel substrate became uneven and porous. The results of the present work demonstrated that elements Si, Ni, and Cr diffused from the Fe2O3 and Fe3O4 layers into the FeO layer have significant effects on 300 M steel in terms of the oxidation kinetics, morphology characterization, and the formation mechanism of the oxide scale by impeding the outward diffusion of iron cations and the inward diffusion of O2-. However, the effect changed with the appearance of molten FeO-Fe2SiO4 eutectic in the FeO layer when 300 M steel was oxidized at 1200 ℃.

Investigation of wear and friction characteristic of Al/(Si3N4)np nano composites under as-cast and heat-treated conditions

Several automotive components, such as clutch plate, piston and cylinder liner, etc., require excellent wear characteristics. The current study focused on fabricating nano Si3N4 reinforced Al alloy composites through a stir casting route with ultrasonic assistance, then performing T-6 heat treatment to alter their properties. Dry sliding wear tests were performed to investigate the frictional and wear characteristics at various applied loads and sliding distances. Results reveal that the coarse grain of α-Al was significantly refined after incorporating nano Si3N4 particles in it, and their structure was transformed from coarse columnar to rosette-like dendrites. The hardness and wear resistance increase with nano Si3N4 addition and T-6 heat treatment. The formation of SiO2 and Fe2O3 layers at the interacting interface significantly reduces the coefficient of friction of nanocomposites. The volumetric loss increased with load (15 N to 45 N) and sliding distance (500 m to 3000 m) for cast and heat-treated samples. The maximum volumetric loss was found in the case of as-cast alloy and the minimum for heat-treated Al/2wt.% Si3N4 nanocomposites. The SEM investigation of worn surfaces shows that the adhesive mechanism is more dominant in alloys, whereas the abrasive wear mechanism was associated with nanocomposites.

Fe3O4 thin films epitaxially growth model on TiO2-terminated SrTiO3(100)

The advanced interface of Fe 3 O 4 /SrTiO 3 , popular in spintronic, has attracted considerable attention. Some experiments have given controversial results on the structure at the Fe 3 O 4 /SrTiO 3 (100) interface. One opinion suggests the formation of interfacial antiferromagnetic FeO layers, while another opinion suggests that are γ-Fe 2 O 3 layers. Here, we propose a theoretical model that what kind of iron oxide stacking sequence forming on the substrate depends on the substrate termination charge. We give a tentative and easy-to-understand growth model for epitaxy, which agrees with the opinion of γ-Fe 2 O 3 layers formation at the Fe 3 O 4 /SrTiO 3 (100) interface. This theoretical model agrees well with the experimental curve and gives a prediction for the different Fe ions concentration depending on thickness. The calculation results of the Fe ions concentration adjacent to the substrate surface show that there are almost no B-site Fe ions at the interface. It indicates that there are unusual electric and magnetic properties at interface. Our growth model illustrates that the possible magnetically dead layer at the interface is responsible for the decrease of the magnetization in the thin films. • This growth mode give credit to the results of interfacial ferrimagnetic γ-Fe 2 O 3 layer in Fe 3 O 4 /SrTiO 3 (100). • The theoretical model curve agrees with the experimental curve, gives prediction for the Fe ions concentration depending on thickness. • The calculation result shows there are almost no B-site Fe at interface. This indicates that there are unusual electric and magnetic properties at interface. The present growth illustrates there exists possible magnetically dead layer at the interface. • It is proposed that the growth mode and the oxidation level are determined by the TiO 2 -termination charge. • The phenomenon that magnetite film grown on SrTiO 3 (001) exhibited vertical compressive and lateral tensile strain, which contradicted the expected behavior, has been explained.

Orthogonal interlayer coupling in an all-antiferromagnetic junction

In conventional ferromagnet/spacer/ferromagnet sandwiches, noncollinear couplings are commonly absent because of the low coupling energy and strong magnetization. For antiferromagnets (AFM), the small net moment can embody a low coupling energy as a sizable coupling field, however, such AFM sandwich structures have been scarcely explored. Here we demonstrate orthogonal interlayer coupling at room temperature in an all-antiferromagnetic junction Fe2O3/Cr2O3/Fe2O3, where the Néel vectors in the top and bottom Fe2O3 layers are strongly orthogonally coupled and the coupling strength is significantly affected by the thickness of the antiferromagnetic Cr2O3 spacer. From the energy and symmetry analysis, the direct coupling via uniform magnetic ordering in Cr2O3 spacer in our junction is excluded. The coupling is proposed to be mediated by the non-uniform domain wall state in the spacer. The strong long-range coupling in an antiferromagnetic junction provides an unexplored approach for designing antiferromagnetic structures and makes it a promising building block for antiferromagnetic devices.

Defective Fe3O4‐x Few‐Atom Clusters Anchored on Nitrogen‐Doped Carbon as Efficient Oxygen Reduction Electrocatalysts for High‐Performance Zinc–Air Batteries

It remains a challenge to develop cost-effective, high-performance oxygen electrocatalysts for rechargeable metal-air batteries. Herein, zinc-mediated zeolitic imidazolate frameworks are exploited as the template and nitrogen and carbon sources, onto which is deposited a Fe3 O4 layer by plasma-enhanced atomic layer deposition. Controlled pyrolysis at 1000°C leads to the formation of high density of Fe3 O4- x few-atom clusters with abundant oxygen vacancies deposited on an N-doped graphitic carbon framework. The resulting nanocomposite (Fe3 O4- x /NC-1000) exhibits a markedly enhanced electrocatalytic performance toward oxygen reduction reaction in alkaline media, with a remarkable half-wave potential of +0.930V versus reversible hydrogen electrode, long-term stability, and strong tolerance against methanol poisoning, in comparison to samples prepared at other temperatures and even commercial Pt/C. Notably, with Fe3 O4- x /NC-1000 as the cathode catalyst, a zinc-air battery delivers a high power density of 158mW cm-2 and excellent durability at 5mA cm-2 with stable 2000 charge-discharge cycles over 600 h. This is ascribed to the ready accessibility of the Fe3 O4- x catalytic active sites, and enhanced electrical conductivity, oxygen adsorption, and electron-transfer kinetics by surface oxygen vacancies. Further contributions may arise from the highly conductive and stable N-doped graphitic carbon frameworks.

High-performance photocatalytic degradation of NiO nanoparticles embedded on α-Fe2O3 nanoporous layers under visible light irradiation

Thin layers of pure Fe2O3 and modified by polyvinyl alcohol (PVA) were synthesized by sol gel route. The morphology of Fe2O3 was modified by the creation of pores by evaporating the Polyvinyl alcohol at 550 °C. This modified structure improved the removal rate of methylene blue (MB) dye aqueous solution under visible irradiation in 10%. The effect of sensitization ratio of NiO nanoparticles onto Fe2O3/PVA (porous) showed very good degradation efficiency up to 100%. Characterization of Fe2O3, Fe2O3 modified by PVA (Fe2O3/PVA), Fe2O3/PVA/NiO have been used such as X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM), UV–Vis … etc. The kinetic parameters of MB elimination by Fe2O3, Fe2O3/PVA and Fe2O3/PVA/NiO were calculated using linear models such as pseudo-first order (PFO), pseudo-second order (PSO) and Elovich. Four error functions were used namely, correlation coefficients (R2), Root Mean Square Error (RMSE), Mean Square Error (MSE) and Sum Squares Error (SSE), to better fit the kinetic equation. The MB elimination mechanism has been studied based on the intra-particle diffusion equation. The effect of pH on the MB removal rate by the two most active catalysts, Fe2O3/PVA and Fe2O3/PVA/with 1%wt. NiO nanoparticles, as well as the pHPZC point were evaluated.

Enabling Long Cycle Life and High Rate Iron Difluoride Based Lithium Batteries by In Situ Cathode Surface Modification.

Metals fluorides (MFs) are potential conversion cathodes to replace commercial intercalation cathodes. However, the application of MFs is impeded by their poor electronic/ionic conductivity and severe decomposition of electrolyte. Here, a composite cathode of FeF2 and polymer‐derived carbon (FeF2@PDC) with excellent cycling performance is reported. The composite cathode is composed of nanorod‐shaped FeF2 embedded in PDC matrix with excellent mechanical strength and electronic/ionic conductivity. The FeF2@PDC enables a reversible capacity of 500 mAh g–1 with a record long cycle lifetime of 1900 cycles. Remarkably, the FeF2@PDC can be cycled at a record rate of 60 C with a reversible capacity of 107 mAh g–1 after 500 cycles. Advanced electron microscopy reveals that the in situ formation of stable Fe3O4 layers on the surface of FeF2 prevents the electrolyte decomposition and leaching of iron (Fe), thus enhancing the cyclability. The results provide a new understanding to FeF2 electrochemistry, and a strategy to radically improve the electrochemical performance of FeF2 cathode for lithium‐ion battery applications.

Oxidation Behavior of Intermetallic Phase and Its Contribution to the Oxidation Resistance in Fe-Cr-Zr Ferritic Alloy

Oxidation resistance of the ferritic Fe-Cr-W-Zr alloy with dispersed Fe2Zr phase were investigated in stagnant air and in static oxygen-saturated liquid Pb-Bi eutectic separately considering the service environment in the advanced generation IV nuclear reactors. A duplex structure including an outer Fe2O3 layer and an inner (Fe,Cr,Zr)2O3 layer is developed after oxidation in air, while a three-layered structure consisting of outer magnetite layer, inner Fe-Cr spinel layer, and internal oxidation zone is formed after oxidation in liquid Pb-Bi eutectic. The dispersed Fe2Zr phase shows delayed oxidation with respect to the α-Fe in air and in liquid Pb-Bi eutectic, which significantly affects the oxidation behaviors of the alloy. After oxidation in air at 923 K, the incorporated Fe2Zr phase in the scale would obstruct the diffusion of metal/oxygen across the scale, resulting in the nonuniform oxidation behavior. After oxidation in static oxygen-saturated liquid Pb-Bi eutectic at 823 K, a reduction in the Fe supply to the magnetite/Fe-Cr spinel interface is present adjacent to the Fe2Zr phase, which might lead to the creation of cavities in the outer magnetite layer with prolonged oxidation time.

Effect of thermal cycling on the corrosion behaviour of stainless steels and Ni-based alloys in molten salts under air and argon

High temperature corrosion of materials in molten salt is of great interest to renewable energy production industry, especially the wide application of molten salts as thermal energy transfer fluid and storage media in concentrated solar power plants. Molten nitrate salt is used in concentrated solar power plants due to its good balance of thermo-physical properties and cost. Storage tanks and heat transfer pipes are widely made of corrosion resistance alloys such as austenitic stainless steels and nickel-based alloys. The corrosion issues between salt-metal interface poses a critical challenge to safety operation and efficiency. In this study, the corrosion behaviour of stainless steels and Ni-based alloys; AISI 321 and 347, IN 625 and In 825, in Solar (nitrate) salts has been experimentally investigated under isothermal (at 565 °C) and thermal cycling (between 565 °C and 290 °C) conditions, and under air and argon atmosphere. Corrosion assessment of test alloys were achieved using gravimetric measurement in a simulated metal-salt environment in a furnace for 14 days. The micro-morphology and cross-sectional analysis of the corroded surfaces were investigated by a combination of scanning electron microscopy, energy dispersive X-ray diffraction techniques. Compared with isothermal condition in air, thermal cycling in air reduces the corrosion rate of test materials, the severity of corrosion attack and the thickness of corrosion product layers due to the lower exposure time at maximum temperature and cooling effect during thermal cycling, especially in stainless steels. Compared with thermal cycling in air, the obtained corrosion rate was observed to be higher for thermal cycling in argon due to the formation of thick and fragile outer layer of NaFeO2 that easily spalls during the corrosion process. A more resilient and potentially more protective inner layer of Cr2O3 and NiO are observed to form in stainless steels and nickel alloys respectively. The formation of intermediate layer of Fe2O3 is believed to offer some barrier to potential molten salt induced dissolution of the inner Cr and Ni-rich layer.

A portable solar light-driven biophotoelectrocatalytic system for pollutant removal powered by photovoltaic cells

Photoelectrocatalytic (PEC) technology has been considered as one of the most efficient advanced oxidation processes for wastewater treatment, but the necessity of external electric power supply limits the portability of PEC system for on-field applications. Herein, a portable solar-powered biophotoelectrocatalytic system driven by photovoltaic (PV) cells was explored for degradation of pollutant by coupling BiVO4/Fe2O3-deposited photoanode and horseradish peroxidase (HRP)-immobilized cathode. The integration of PV cells in this PEC device could not only avoid the necessary introduction of external electric power supply, but also improve the utilization of solar irradiation. The characterization of BiVO4/Fe2O3 photoanode demonstrates that ultrathin Fe2O3 layer on BiVO4 electrode could facilitate the holes transfer to the surface efficiently and thus avoid charge recombination. After HRP was immobilized on the cathode, the removal efficiency for 2,4-dichlorophenol (2,4-DCP) was obviously promoted, attributed to the efficient HRP-catalyzed oxidation reaction by in-situ generated H2O2 from PEC process. Under natural solar irradiation, the proposed portable biophotoelectrocatalytic device exhibited a satisfying removal efficiency of 92.0% for 100 ppm of 2,4-DCP after 3-h treatment. The intermediate products formed during the degradation process were identified by liquid chromatography-mass spectrometry, and possible 2,4-DCP degradation pathway was also proposed.

Investigation of optical, structural, and electrical properties of heterostructure Fe2O3 deposited by RF magnetron sputtering on ZnO layer by spray pyrolysis

In this study, firstly, ZnO thin film was produced on glass substrate by chemical spray pyrolysis method at 450 °C and then Fe2O3 layer was produced on ZnO substrate thin film by RF magnetron sputtering technique. Fe2O3/ZnO heterostructure was fabricated. The crystal structure, surface morphology and structure, chemical composition, optical and electronic properties, and electric properties of the ZnO and Fe2O3/ZnO samples were performed by X-ray diffraction (XRD), Raman spectrometer, field emission scanning electron microscope (SEM), focused ion beam (FIB) microscope, atomic force microscope (AFM), energy-dispersive X-ray (EDX), ultraviolet–visible spectrophotometer (UV–VIS), and Hall measurements, respectively. XRD and Raman measurements showed that ZnO and Fe2O3 thin films have wurtzite hexagonal and cubic crystal structures, respectively, and both are in polycrystalline form. FE-SEM and cross-sectional FIB-SEM images indicate that Fe2O3 flake-like nano-sized structures are formed on the ZnO substrate. In addition, AFM images revealed that the Fe2O3 nano-sized structure was distributed as nanosheets on the ZnO thin-film surface. UV–VIS measurements of ZnO revealed that the ZnO and Fe2O3/ZnO heterostructure band gap energies were 3.277 eV and 3.24 eV, respectively. Finally, the calculated values of electric conductivity, σ, electron density, n, and electron mobility, μ, using the data obtained from Hall measurements are 4.39 × 102 Ω−1 m−1, 6.88 × 1021 m−3, and 3.99 × 10–1 V−1m2s, respectively.

Superassembled Hierarchical Asymmetric Magnetic Mesoporous Nanorobots Driven by Smart Confined Catalytic Degradation.

Micro/nanoscale robotics has received great attention in many important fields. However, it is still a great challenge to construct nanorobots simultaneously possessing multifunctionality, well-controlled directionality, and fast and durable motion as well as fully compatible and biodegradable components. Here, a hierarchical, asymmetric, hollow, catalytic, magnetic, and mesoporous nanorobot has been fabricated through a multistep interfacial superassembly strategy. The multilayer composites consist of hollow silica nanoflasks sequentially coated with a highly magnetic responsive Fe3 O4 layer, a mesoporous silica layer with homogeneous vertical channels, and a layer of catalytic gold nanoparticles on both the inner and outer surfaces. Furthermore, para-nitrophenol was used as a model pollutant to trigger self-motility of the nanoflasks by confined catalytic degradation (CCD). We found that the bottleneck morphology and mesoporous surface both improved the catalytic nanoparticle loading capability and CCD effect, thus enabling efficient self-motility and a durable movement capacity of ∼100 h. In addition, the catalytic performance was improved by 180 % compared with that of solid spherical nanoparticles.

Remarkably high capacity Li ion batteries with rf sputter deposited TiO2 thin film anodes on SS substrates

TiO2 thin film electrodes have been prepared using radio-frequency magnetron sputtering technique on polished stainless-steel substrates. Films with amorphous, anatase and rutile phases have been obtained by varying the preparation conditions and coin cell type Lithium Ion Batteries (LIB’s) have been prepared with these samples as anodes. During the cycling test, all the samples show a gradual increase in capacity with increasing no. of charging/discharging cycles after an initial decrease with the cell containing the rutile phase TiO2 showing the highest specific capacity of around 1.217 mAh.cm-2.μm−1 after 1000 cycles at a high current density of 0.127 mA.cm−2, which is better than any reported value so far. Structural and morphological investigations of the samples by various techniques show that a synergy between the deposited TiO2 film and the Fe2O3 layers present on the SS substrate alongwith an increase in porosity in the films during the charge–discharge cycling gives rise to the remarkably high capacity of the cells which increases gradually with cycling. The present study shows that LIB’s with composite TiO2/Fe2O3 anode having advantage of structural stability of TiO2 and better diffusion kinetics of Fe2O3 can be obtained by a simple, easily scalable, reproducible rf magnetron sputtering technique and specific capacities of the present LIB’s are comparable to or better than that obtained through much more complicated and multi-step chemical processes and hence the results are important for large scale technological applications.

Role of oxygen vacancies in colossal polarization in SmFeO3-δ thin films.

The orthorhombic rare-earth manganates and ferrites multiferroics are promising candidates for the next generation multistate spintronic devices. However, their ferroelectric polarization is small, and transition temperature is far below room temperature (RT). The improvement of ferroelectricity remains challenging. Here, through the subtle strain and defect engineering, an RT colossal polarization of 4.14 μC/cm2 is achieved in SmFeO3-δ films, which is two orders of magnitude larger than its bulk and is also the largest one among the orthorhombic rare-earth manganite and ferrite family. Meanwhile, its RT magnetism is uniformly distributed in the film. Combining the integrated differential phase-contrast imaging and density functional theory calculations, we reveal the origin of this superior ferroelectricity in which the purposely introduced oxygen vacancies in the Fe-O layer distorts the FeO6 octahedral cage and drives the Fe ion away from its high-symmetry position. The present approach can be applied to improve ferroelectric properties for multiferroics.

Strain-Induced Magnetoelectric Coupling in Fe3O4/BaTiO3 Nanopillar Composites.

Magnetoelectric coupling properties are limited to the substrate clamping effect in traditional ferroelectric/ferromagnetic heterostructures. Here, Fe3O4/BaTiO3 nanopillar composites are successfully constructed. The well-ordered BaTiO3 nanopillar arrays are prepared through template-assisted pulsed laser deposition. The Fe3O4 layer is coated on BaTiO3 nanopillar arrays by atomic layer deposition. The nanopillar arrays and heterostructure are confirmed by scanning electron microscopy and transmission electron microscopy. A large thermally driven magnetoelectric coupling coefficient of 395 Oe °C-1 near the phase transition of BaTiO3 (orthorhombic to rhombohedral) is obtained, indicating a strong strain-induced magnetoelectric coupling effect. The enhanced magnetoelectric coupling effect originated from the reduced substrate clamping effect and increased the interface area in nanopillar structures. This work opens a door toward cutting-edge potential applications in spintronic devices.