Multiferroic Bismuth Ferrite Research Articles

Electrical Quantum Coupling of Subsurface-Nanolayer Quasipolarons.

We perform dielectric and impedance spectrums on the compressively-strained ceramics of multiferroic bismuth ferrite. The subsurface-nanolayer quasipolarons manifest the step-like characteristic of pressure-dependent transient frequency and, furthermore, pressure-dependency fails in the transformation between complex permittivity and electrical impedance, which is well-known in classic dielectric physics, as well as the bulk dipole chain at the end of the dissipation peak.

Enhanced Dielectric Constant of PVDF-HFP/BFO Composite Films for Ferroelectric Applications

We have developed multiferroic Bismuth ferrite (BiFeO3, BFO) incorporated Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer-ceramic composites through the solution casting method. The polymer-ceramic composites are fabricated by varying the composition of the BFO as a filler material ranging 5, 10, 15, 20, 25, 30, and 40 wt% into the PVDF-HFP polymer matrix. We have investigated the effect of BFO loading on the structural, morphological, spectroscopic, and dielectric properties by different characterization techniques. X-ray diffraction analysis indicates the presence of non-polar α- and polar β- phases of PVDF-HFP in the composites. Scanning electron microscope studies revealed the spherulite morphology and homogenous dispersion of BFO particles. The addition of BFO filler in PVDF-HFP matrix at various percentages has been studied to improve the polar β- phase of PVDF-HFP which may enhance ferroelectric properties. The dielectric studies at room temperature showed an increase in dielectric constant value from 9.5 (pure PVDF-HFP) to 21.08 (30% loaded BFO) at 100 Hz. It is also evident from the Fourier Transform- Infrared (FT-IR) spectra, that a maximum of 75.24% of β-fraction is observed for 30% loaded BFO composition. The enhanced properties of the fabricated materials suggest that they may be useful for polymer-ceramic capacitor applications. The results are discussed in detail.

Subnanosecond Reconfiguration of Ferroelectric Domains in Bismuth Ferrite.

Domain switching is crucial for achieving desired functions in ferroic materials that are used in various applications. Fast control of domains at subnanosecond timescales remains a challenge despite its potential for high-speed operation in random-access memories, photonic, and nanoelectronic devices. In this work, ultrafast laser excitation is shown to transiently melt and reconfigure ferroelectric stripe domains in multiferroic bismuth ferrite on a timescale faster than 100ps. This dynamic behavior is visualized by picosecond- and nanometer-resolved X-ray diffraction measurements as well as time-resolved X-ray diffuse scattering. The disordering of stripe domains is attributed to the screening of depolarization fields by photogenerated carriers resulting in the formation of charged domain walls, as supported by phase field simulations. Furthermore, the recovery of disordered domains exhibits subdiffusive growth on nanosecond timescales, with a nonequilibrium domain velocity reaching up to 10 m/s. These findings present a new approach to image and manipulate ferroelectric domains on subnanosecond timescales, which can be further extended into other photoferroic systems to modulate their electronic, optical, and magnetic properties beyond GHz frequencies. This approach could pave the way for high-speed ferroelectric data storage, computing and photonic applications in a range of photoferroics, and, more broadly, defines new approaches for visualizing the non-equilibrium dynamics of heterogeneous and disordered materials. This article is protected by copyright. All rights reserved.

Multiferroic behavior of room temperature bismuth ferrite with tailored calcination temperature

One of the few materials that is multiferroic (antiferromagnetic and ferroelectric) is bismuth ferrite. In this study, we used the sol-gel method to create multiferroic bismuth ferrite and examined its structural and optical characteristics. The annealing temperature used to create bismuth ferrite was 600°C. The rhombohedral crystal structure was revealed by X-ray diffraction (XRD) investigation. The XRD diffractogram data examines the phase and planes of orientation for the synthesized materials. The crystalline size for the peak was determined using the Scherrer equation. Analysis using the Fourier transform infrared (FTIR) confirmed the existence of M-O octahedral and tetrahedral coordinates of the M-O bonds formed. The Fourier transform infrared in the wavenumber range of 500–850 cm−1 has been used to study the vibrational modes of the octahedral and tetrahedral metal complexes in the sample. Studies using a FESEM show that the synthesized nanocomposite has morphological characteristics, including interconnected agglomerates with spherical, irregular, or non-uniform elongated forms. By increasing the loading percentage of bismuth ferrite, the composite remnant magnetization (Mr) and saturation magnetization (Ms) values were discovered to be 0.43701 emu/g and 0.1940 emu/g, respectively. A frequency range of 10 Hz to 106 Hz was used to study the dielectric measurement of the nanocomposites. In the temperature range of 310 to 525 K, the AC conductivity has been measured, and it has been discovered that conductivity decreases as temperature rises. A temperature increase results in a reduction in the dielectric constant and dielectric loss. The initial data imply that the nanocomposite is a possible contender for use in capacitors with high dielectric constants. The composite will be useful for usage in hard disc components due to its magnetic characteristics, which is significant.

Barium and Yttrium Co-doping in Bismuth Ferrite Nanoparticles to Enhance Microwave Properties

The microwave properties of multiferroic Bismuth Ferrite have been widely studied and focus has been placed on the improvement of microwave absorption, impedance matching, effective bandwidth through doping with suitable elements, and formation of nanostructures. In this work, Barium and Yttrium co-doping at the Bi site of BiFeO3 nanoparticles (BayBi1-x-yYxFeO3) were observed to be effective in enhancing the dielectric and magnetic properties of the sample with x = 0.03 and y = 0.1. A minimum reflection loss of −61.7 dB was achieved in the sample for a composite absorber length of 7.5 mm attributed to the best balance observed between dielectric loss (tanδ ε ) and magnetic loss (tanδ μ ) based on the match equation, tanδ ε = tanδ μ . The best impedance matching observed in this sample also supports the observed high microwave absorption required for practical application as microwave absorption material.

Bismuth ferrite (BiFeO3) 2D-nanoflakes for the photocatalytic degradation of chromogenic dyes under solar irradiation

Two-dimensional (2D) nanostructures show interesting properties compared to other low-dimensional nanostructures due to their pronounced anisotropic features governing the physicochemical properties of materials. In this context, multiferroic bismuth ferrite (BiFeO3/BFO) nanostructures are developed via a facile hydrothermal process by varying the surfactants leading to 3D nanoparticulate and 2D nanoflaky structures with dimensions in the range of 50–100 nm. The developed materials are characterized for their structural, morphological, optical and surface properties using XRD, Rietveld refinements, XPS, FTIR, UV–Vis, PL and BET techniques. The optimization studies by varying the concentration of dye (5, 10, 15, 20 ppm) and photocatalyst (25, 50, 75 and 100 mg) suggest that 10 ppm of dye and 50 mg of photocatalyst concentration is optimal, which showed around 98% and 96% degradation of chromogenic methyl orange and crystal violet dye molecules, respectively within 120 min. The insights from UV–Vis, PL, Mott-Schottky analysis, photocurrent and electrochemical impedance suggested that the opto-electronic properties of BFO are meaningly improved due to its 2D-flaky anisotropic features compared to 3D isotropic particulate structure. The radical detection experiment revealed that the dye degradation is mediated by advanced oxidation process via high energetic hydroxyl radicals driven by the improved ferroelectricity-mediated band-bending and internal electrical fields in BFO flakes compared to particles. Magnetic studies by VSM showed that the BFO flakes manifest enhanced ferromagnetic properties compared to particles contribute to both catalytic activity as well as its easy catalyst-recovery with minimal loss. The recycle experiments confirmed that the BFO-flakes are photochemically stable for prolonged use for industrial application.

Dielectric Relaxation Behavior and Conduction Mechanism of Ca and Ti Co-Doped Multiferroic Bismuth Ferrite

Dielectric Relaxation Behavior and Conduction Mechanism of Ca and Ti Co-Doped Multiferroic Bismuth Ferrite

МАГНИТОЭЛЕКТРИЧЕСКИЕ ЭФФЕКТЫ И НОВЫЕ ЛОГИЧЕСКИЕ УСТРОЙСТВА СПИНТРОНИКИ

The paper discusses new logic spintronic devices and the prospects for the use of perovskite-type multiferroics as working elements of magnetoelectric components. The principle of operation of the considered logical devices is based on the use of two components - a magnetoelectric, in which the magnetic state is recorded due to energy-efficient magnetoelectric interaction, and a spin-orbital component, in which information is read out based on the conversion of spin into charge due to the spin-orbital interaction of electrons; both components are interconnected by a nanoelectrode. When designing new logic spintronic devices, it is necessary to take into account the effectiveness of the mechanisms of ME interactions; features of spin - polarized currents and associated torques influencing magnetic moments; as well as other factors affecting the speed of switching magnetic states and the sensitivity of the device to external agents. Multiferroic materials that are promising for use as elements of ME components of new logic devices must meet a number of requirements, the most significant of which are the magnitude of the magnetoelectric coupling coefficient and the temperature at which ME effects occur. The paper considers representatives of multiferroics with a perovskite structure that meet these conditions, to some extent partially, these are high-temperature multiferroic bismuth ferrite (BiFeO3) and Ruddlesden-Popper structures, in which high-temperature ferroelectric effects are already realized and under certain conditions an ME effect is possible. The crystal structure of these compounds is considered, and the role of crystallographic distortions responsible for the manifestation of magnetoelectric properties is analyzed. Expressions are obtained for the tensor of the magnetoelectric effect as functions of magnetic order parameters, and the fundamental possibility of realizing ME effects in Ruddlesden-Popper structures containing magnetic cations is shown.

Analysis of conductivity and band-gap energy of bismuth ferrite nanoparticles as prospective photovoltaic material

Photovoltaic solar cell converts the radiation of sun to electric charge that is a sustainable tool for harvesting renewable energy. Multiferroic bismuth ferrite (BFO) nanoparticles consist of low band-gap energy that proclaims highly promising photovoltaic cells material. The Sol-gel procedure derived nanocrystalline bismuth ferrite (BFO) powders for investigation during the research. X-ray diffractometry (XRD) implementation provided desired output, depicting the crystalline structure and bond formation of sample BFO nano-particles. Field emission scanning electron microscope (FESEM) laid out the proper morphology and sampled BFO powders' structural composition. Application of heat was varied from 50 to 175 °C temperature range upon the synthesized BFO samples. BFO consists of low band-gap energy and lesser efficiency (<2%), proving it to be unfit for practical appliances, even though BFO asserts highly promising photovoltaic characteristics. The dimension of the crystallized structures is 48.71 nm. The morphology of BFO nanoparticles, determined by FESEM microscopic inspection, has been 166.39 nm. The direct as well as indirect band-gap energies, respectively 2.10 and 2.09 eV, indicate the prospective future of BFO as a photovoltaic material. Analysis of the lowest and highest applied temperatures illustrated the conspicuous change in conductivity. Where an increase in temperature seemed to improve the value of conductivity consequently. Band-gap energy was measured and found to be a promising value for a Photovoltaic material.

Enhancement of weak ferromagnetism, exotic structure prediction and diverse electronic properties in holmium substituted multiferroic bismuth ferrite.

Bismuth ferrite (BFO, BiFeO3), exhibiting both ferromagnetic and ferroelectric properties at room temperature, is one of the most researched multiferroic materials with a growing number of technological applications. In the present study, using a combined theoretical-experimental approach, we have investigated the influence of Ho-doping on the structural, electronic and magnetic properties of BFO. Synthesis and structural XRD characterization of Bi1-xHoxFeO3 (x = 0.02, 0.05, and 0.10) nanopowders have been completed. After structure prediction of Ho-doped BiFeO3 using bond valence calculations (BVC), six most favorable candidates were found: α-, β-, γ-, R-, T1, and T2. Furthermore, all structure candidates have been examined for different magnetic ordering using DFT calculations. The magnetic behavior of the synthesized materials was investigated using a SQUID magnetometer equipped with an oven. The plethora of magnetic and electronic properties of the Ho-doped BFO that our theoretical research predicted can open up rich possibilities for further investigation and eventual applications.

Brief Theoretical Overview of Bi-Fe-O Based Thin Films.

This paper will provide a brief overview of the unique multiferroic material Bismuth ferrite (BFO). Considering that Bismuth ferrite is a unique material which possesses both ferroelectric and magnetic properties at room temperature, the uniqueness of Bismuth ferrite material will be discussed. Fundamental properties of the material including electrical and ferromagnetic properties also will be mentioned in this paper. Electrical properties include characterization of basic parameters considering the electrical resistivity and leakage current. Ferromagnetic properties involve the description of magnetic hysteresis characterization. Bismuth ferrite can be fabricated in a different form. The common forms will be mentioned and include powder, thin films and nanostructures. The most popular method of producing thin films based on BFO materials will be described and compared. Finally, the perspectives and potential applications of the material will be highlighted.

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.

Temperature dependence of the local electromagnetic field at the Fe site in multiferroic bismuth ferrite

In this paper, we present a study of the temperature-dependent characteristics of electromagnetic fields at the atomic scale in multiferroic bismuth ferrite (${\mathrm{BiFeO}}_{3}$ or BFO). The study was performed using time differential perturbed angular correlation (TDPAC) spectroscopy on implanted $^{111}\mathrm{In}$ ($^{111}\mathrm{Cd}$) probes over a wide temperature range. The TDPAC spectra show that substitutional $^{111}\mathrm{In}$ on the ${\mathrm{Fe}}^{3+}$ site experiences local electric polarization, which is otherwise expected to essentially stem from the ${\mathrm{Bi}}^{3+}$ lone pair electrons. Moreover, the TDPAC spectra show combined electric and magnetic interactions below the N\'eel temperature ${T}_{N}$. This is consistent with simulated spectra. X-ray diffraction (XRD) was employed to investigate how high-temperature TDPAC measurements influence the macroscopic structure and secondary phases. With the support of ab initio DFT simulations, we can discuss the probe nucleus site assignment and can conclude that the $^{111}\mathrm{In}$ ($^{111}\mathrm{Cd}$) probe substitutes the Fe atom at the B site of the perovskite structure.

Importance of the Hubbard U parameter to explore accurate electronic and optical behaviour of BiFeO3

Based upon Hubbard U corrected density functional theory (DFT), the electronic and optical responses of multiferroic Bismuth ferrite (BiFeO3; BFO) have been critically explored. Treating BFO as a strongly correlated insulating system, a Hubbard U parameter is considered for accurate description of localised Fe-3d states. However, the U parameter for the Fe-3d state is not sufficient as 2p states of O atoms are greatly influenced by Fe-3d states. Similar U parameters for Fe-3d as well as O-2p states are considered. An effective U value around 4.3 eV not only solves the band gap mismatch of BFO from both a theoretical and experimental aspect, but also predicts the exact nature of the band gap. Moreover, within this framework, the optical responses of BFO are critically investigated. Multiple transitions appearing in both theoretical and experimental absorption spectra are well explained by crystal field transitions of Fe3+ ions in a d5 high spin state, supported by the density of states curve of BFO. Therefore, based upon the DFT + U approach, accurate electronic and optical characteristics of BFO are critically explored, which is essential for its multidirectional application perspectives.

An investigation of elastic and attenuation properties of Gd-doped multiferroic bismuth ferrites

An investigation of elastic and attenuation properties of Gd-doped multiferroic bismuth ferrites

Analysis of size-dependent variation in nonlinear absorption coefficient of multiferroic bismuth ferrite nanoparticles synthesized at different sintering temperature

Third-order nonlinear optical property of multiferroic bismuth ferrite (BiFeO3) nanoparticles sintered at different temperatures has been studied by employing Z-Scan technique. BiFeO3 (BFO) nanoparticles (NPs) were synthesized by the sol–gel process with different sintering temperature of 823[Formula: see text]K, 923[Formula: see text]K and 1023[Formula: see text]K. XRD reveals that all samples have single-phase rhombohedral structure with R3c space group with no secondary phases present. The calculated crystallite size for samples sintered at 823[Formula: see text]K, 923[Formula: see text]K and 1023[Formula: see text]K is found to be 75[Formula: see text]nm, 87[Formula: see text]nm and 94[Formula: see text]nm, respectively. Crystal structure parameters and phase analysis of the BFO samples are obtained by the Rietveld refinement (FullProf) method. FTIR spectra show the absorbance peaks at 448[Formula: see text]cm[Formula: see text] and 533[Formula: see text]cm[Formula: see text] which confirm the synthesis of NPs. SEM images show the agglomerated spherical particles. Average crystallite and particle size of the samples are found to increase by increasing the sintering temperature. EDX verifies the constituent elements and reveals that stoichiometry in sample preparation is well-matched with the atomic ratio of the experimental quantity. The nonlinear absorption coefficient is characterized by the Z-Scan method employing continuous wave (CW) laser operating at 532[Formula: see text]nm wavelength. Nonlinear absorption coefficient ([Formula: see text]), evaluated by open aperture Z-scan data, is found to decrease with an increase in the particle size of the BFO NPs. BFO nanoparticles synthesized by optimizing the synthesis temperature can be used for the various applications of futuristic multiferroic and optical devices.

First-principles calculations to investigate the structural and electronic properties of BFO through doping of holmium atom(s)

Multiferroic bismuth ferrites and holmium doped bismuth ferrites are simulated using density functional theory and first principles studies are conducted as a preliminary attempt to observe the possible modifications with doping. The unit cell of pure and doped bismuth ferrites and corresponding Brillouin zones are simulated. Band structure and density of states are computed using CASTEP and DMol3 analysis. The smaller band gap and shifting in density states are noticed with the influence of holmium addition in Bi-site, along with the transition from direct to the indirect bandgap. The tunability of these properties with doping can suggest the application possibilities of BFO in different areas, especially in optical devices, photovoltaics, and photocatalysts.

Optical and electrical properties of impurity-less multiferroic bismuth ferrite nanoparticles

Synthesis of high-purity multiferroic bismuth ferrite (BFO) nanoparticles is a big challenge for researchers. In this research, we synthesized high-purity BFO nanoparticles by a modified sol-gel method. BFO nanoparticles were characterized for structural, morphological, optical, electrical, and multiferroic properties. The Rietveld refinement revealed the rhombohedral crystal structure with R3c space group and devoid of impurity phases. Measured average particle size from FESEM and TEM images were 152 and 148 nm, respectively. The ferroelectric and ferromagnetic properties of synthesized nanoparticles were investigated in detail. The leakage current density and the space-charge-limited current were analyzed to study the effect of impurities. The dielectric properties were measured and characterized for dielectric constant, dielectric loss, resistance, reactance, impedance, resistivity, conductivity, electric modulus, and Cole-Cole plot. The calculated optical bandgap energy from UV–Vis–NIR spectroscopy and photoluminescence spectroscopy were 2.057 eV and 2.087 eV, respectively.

Integrating Band Engineering and the Flexoelectric Effect Induced by a Composition Gradient for High Photocurrent Density in Bismuth Ferrite Films.

Photovoltaic energy as one of the important alternatives to traditional fossil fuels has always been a research hot spot in the field of renewable and clean solar energy. Very recently, the anomalous ferroelectric photovoltaic effect in multiferroic bismuth ferrite (BiFeO3) has attracted much attention due to the above-bandgap photovoltage and switchable photocurrent. However, its photocurrent density mostly in the magnitudes of μA/cm2 resulted in a poor power conversion efficiency, which severely hampered its practical application as a photovoltaic device. In this case, a novel approach was designed to improve the photocurrent density of BiFeO3 through the cooperative effect of the gradient distribution of oxygen vacancies and consequently induced the flexoelectric effect realized in the (La, Co) gradient-doped BiFeO3 multilayers. Subsequent results and analysis indicated that the photocurrent density of the gradient-doped multilayer BiFeO3 sample was nearly 3 times as much as that of the conventional doped single-layer sample. Furthermore, a possible mechanism was proposed herein to demonstrate roles of band engineering and the flexoelectric effect on the photovoltaic performance of the gradient-doped BiFeO3 film.

Interfacial engineering in 3D/2D and 1D/2D bismuth ferrite (BiFeO3)/Graphene oxide nanocomposites for the enhanced photocatalytic activities under sunlight

3D-particulate and 1D-fiber structures of multiferroic bismuth ferrite (BiFeO3/BFO) and their composites with 2D-graphene oxide (GO) have been developed to exploit the different scheme of interfacial engineering as 3D/2D and 1D/2D systems. Particulates and fibers of BFO were developed via sol-gel and electrospinning fabrication approaches respectively and their integration with GO was performed via the ultrasonic-assisted chemical reduction process. The crystalline and phase formation of BiFeO3 and GO was confirmed from the XRD patterns obtained. The electron microscopic images revealed the characteristic integration of 3D particulates (with average size of 100 nm) and 1D fibers (with diameter of ~150 nm and few μm length) onto the 2D GO layers (thickness of ~27 nm). XPS analysis revealed that the BFO nanostructures have been integrated onto the GO through chemisorptions process, where it indicated that the ultrasonic process engineers the interface through the chemical modification of the surface of these 3D/2D and 1D/2D nanostructures. The photophysical studies such as the impedance and photocurrent measurements showed that the charge separation and recombination resistance is significantly enhanced in the system, which can directly be attributed to the effective interfacial engineering in the developed hetero-morphological composites. The degradation studies against a model pollutant Rhodamine B revealed that the developed nanocomposites exhibit superior photocatalytic activity via the effective generation of OH radicals as confirmed by the radical analysis studies (100% degradation in 150 and 90 min for 15% GO/BFO particulate and fiber composites, respectively). The developed system also demonstrated excellent photocatalytic recyclability, indicated their enhanced stability.