BiFeO3

The electronic structure of BiFeO3 has been investigated by using electron energy loss spectrum and first-principle calculations. Assignments of the individual interband transitions have been accomplished by comparing the interband transition energy with the calculated PDOS. The DOS is mainly divided into two regions, the hybridized region of O 2p with Fe 3p in the valence band and that of O 2p hybridized with Bi 6p in the conduction band. From the simulation of high energy-loss near-edge structure, the core-hole effect is believed to be more significant...

Visible light-responsive Pt-loaded coral-like BiFeO3 (Pt-BFO) nanocomposite at different Pt loadings was synthesized via a two-step hydrothermal synthesis method. The as-synthesized photocatalyst was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and magnetic hysteresis loop (M-H loop) analyses...

The misfit dislocations formed at heteroepitaxial interfaces create long-ranging strain fields in addition to the epitaxial strain. For systems with strong lattice coupling, such as ferroic oxides, this results in unpredictable and potentially debilitating functionality and device performance. In this work, we use dark-field x-ray microscopy to map the lattice distortions around misfit dislocations in an epitaxial film of bismuth ferrite (BiFeO3) - a well-known multiferroic. We demonstrate the ability to precisely quantify weak, long-ranging strain fields and their associated symmetry lowering without modifying the mechanical state of the film...

Nanometer-scale 3D imaging of materials properties is critical for understanding equilibrium states in electronic materials, as well as for optimization of device performance and reliability, even though such capabilities remain a substantial experimental challenge. Tomographic atomic force microscopy (TAFM) is presented as a subtractive scanning probe technique for high-resolution, 3D ferroelectric property measurements. Volumetric property resolution below 315 nm3 , as well as unit-cell-scale vertical material removal, are demonstrated...

Multiferroic BiFeO3 crystals were investigated by means of micro-Raman spectroscopy using the laser wavelengths of 442 nm (resonant conditions) and 633 nm (non-resonant conditions). The azimuthal angle dependence of the intensity of the Raman modes allowed their symmetry assignment. The experimental data are consistent with a simulation based on Raman tensor formalism. Mixed symmetries were taken into account, considering the orientation of the crystal optic axis along a pseudo-cubic <111> direction...

In classical morphotropic piezoelectric materials, rhombohedral and tetragonal phase variants can energetically compete to form a mixed phase regime with improved functional properties. While the discovery of morphotropic-like phases in multiferroic BiFeO3 films broadened this definition, accessing these phase spaces is still typically accomplished through isovalent substitution or heteroepitaxial strain which do not allow for continuous modification of phase composition post-synthesis. Here, we show that it is possible to use low-energy helium implantation to tailor morphotropic phases of epitaxial BiFeO3 films post-synthesis in a continuous and iterative manner...

Electric field control of magnetism ultimately opens up the possibility of reducing energy consumption of memory and logic devices. Electric control of magnetization and exchange bias are demonstrated in all-oxide heterostructures of BiFeO3 (BFO) and La0.7 Sr0.3 MnO3 (LSMO). However, the role of the polar heterointerface on magnetoelectric (ME) coupling is not fully explored. Here, the ME coupling in BFO/LSMO heterostructures with two types of interfaces, achieved by exploiting the interface engineering at the atomic scale, is investigated...

While bismuth ferrite BiFeO3 (BFO) is a well studied multiferroic material, its electronic and magnetic properties in the presence of A-site dopants have not been explored widely. Here we report the results of a systematic study of the local electronic structure, spontaneous polarization, and magnetic properties of lanthanum (La) and strontium (Sr) doped rhombohedral bismuth ferrite within density functional theory. An enhanced ferroelectric polarization of 122.43 μC/cm2 is predicted in the uniformly doped BiLaFe2 O6 ...

Co3 O4 /BiFeO3 nanocomposite catalysts were synthesized by a facile hydrothermal method following the impregnation process. The nanocomposite was successfully characterized by powder X-ray diffraction(XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption desorption isotherms and X-ray photoelectron spectroscopic (XPS) analysis. The as-synthesized Co3 O4 /BiFeO3 nanocomposites were tested as a catalyst in the reduction of nitrophenol isomers with NaBH4 at room temperature...

In data storages, spin, ferroelectric or optical index has been utilized as the information carrier, and the binate couplings among the three parameters are explored to increase the resistance states and resultant data-density. However, studies holding all of the three information indices are still blank, which can offer more resistance states than the binate cases. In this work, using the spin-electron-photon resolved theory, we demonstrate the feasibility of spin, ferroelectric and optical interactions, which are further detected by a spin- and ferroelectric-modulated photovoltaic effect in La2/3Sr1/3MnO3/BiFeO3/Fe4N multiferroic tunnel junctions (MFTJs)...

The structure, magnetic and ferroelectric properties of sputtered epitaxial CoFe2O4-BiFeO3 (CFO-BFO) nanocomposite thin films grown on La0.7Sr0.3MnO3 (LSMO) layers on (001) oriented SrTiO3 (STO) substrates and on STO-buffered Si are described. The as-grown LSMO thin films were smooth and poorly conductive but the resistivity was reduced and the surfaces roughened after annealing. Cosputtered CFO and BFO on STO formed vertically aligned nanostructures consisting of epitaxial spinel CFO pillars within a perovskite BFO matrix, but the rough surface of the annealed LSMO film promoted additional CFO pillar orientations...

Substitution of bismuth by rare-earth (RE) ions is of great technological importance to develop room-temperature BiFeO3-based multiferroic materials. Despite this interest, many fundamental properties and the structure-property correlations of RE-doped BiFeO3 remain poorly understood. Here we report a systematical experimental and theoretical exploration on the structural phase transition in Bi1-xLaxFeO3 (0 ≤ x ≤ 0.2) ceramics. By using x-ray absorption fine structure spectroscopy, we for the first time show that the La3+ dopants in fact substitute the Bi site of a secondary nanosized particles with orthorhombic Pbam symmetry instead of the long-believed parental rhombohedral R3c phase at all La3+ doping concentrations (0...

The properties of magnetic nanocomposites rely strongly on the interplay between those of the constituent components. When the individual components themselves are complex systems belonging to the family of correlated electron oxide systems which typically exhibit exotic physical properties, it becomes nontrivial to customize the properties of the nanocomposite. In this paper, we demonstrate an easy, but effective method to synthesize and tune the magnetic properties of nanocomposites consisting of correlated electron oxide systems as the individual components...

Demonstration of ultralow energy switching mechanisms is imperative for continued improvements in computing devices. Ferroelectric (FE) and multiferroic (MF) order and their manipulation promise an ideal combination of state variables to reach attojoule range for logic and memory (i.e., ~30× lower switching energy than nanoelectronics). In BiFeO3 (BFO), the coupling between the antiferromagnetic (AFM) and FE order is robust at room temperature, scalable in voltage, stabilized by the FE order, and can be integrated into a fabrication process for a beyond-CMOS (complementary metal-oxide semiconductor) era...

Exploring and manipulating the domain configurations in ferroelectric thin films are of critical importance for the design and fabrication of ferroelectric heterostructures with novel functional performance. In this study, BiFeO3 (BFO) ultrathin films with various Bi/Fe ratios from Bi-excess to Bi-deficient have been grown on (La0.7Sr0.3)MnO3 (LSMO) covered SrTiO3 substrates by laser molecular beam epitaxy system. Atomic force microscopy and piezoresponse force microscopy measurements show that both the surface morphology and ferroelectric polarization of the films are relevant to the Bi nonstoichiometry...

Dynamics of domain walls are among the main features that control strain mechanisms in ferroic materials. Here, we demonstrate that the domain-wall-controlled piezoelectric behaviour in multiferroic BiFeO3 is distinct from that reported in classical ferroelectrics. In situ X-ray diffraction was used to separate the electric-field-induced lattice strain and strain due to displacements of non-180° domain walls in polycrystalline BiFeO3 over a wide frequency range. These piezoelectric strain mechanisms have opposing trends as a function of frequency...

Self-assembled heteroepitaxial nanostructures have played an important role for miniaturization of electronic devices, e.g., the ultrahigh density ferroelectric memories, and cause for great concern. Our first principle calculations predict that the materials with low formation energy of the interface ( Ef ) tend to form matrix structure in self-assembled heteroepitaxial nanostructures, whereas those with high Ef form nanopillars. Under the guidance of the theoretical modeling, perovskite BiFeO3 (BFO) nanopillars are swimmingly grown into CeO2 matrix on single-crystal (001)-SrTiO3 (STO) substrates by pulsed laser deposition, where CeO2 has a lower formation energy of the interface ( Ef ) than BFO...

Ordering of cations in different structural types occurs when there is a significant difference in the oxidation states and ionic radii of the ions involved. Herein we report an unusual ordering of isovalent cations Fe3+ and Al3+ in the polar rhombohedral R3 double perovskite structure of Bi2 FeAlO6 synthesized at high-pressure (6 GPa) and high-temperature (1000 °C). This ordered structure is derived from the 1:1 combination of the polar oxides BiFeO3 (R3c) and BiAlO3 (R3c), which results in reduction of symmetry to an R3 structure where the Fe3+ and Al3+ ions are ordered in a rock salt manner...

A novel ternary composite of graphitic carbon nitride (g-C3 N4 )/graphene oxide (GO) sheets/BiFeO3 (CNGB) with highly enhanced visible-light photocatalytic activity toward Cr(VI) photoreduction is prepared and characterized. The characterization and photocatalysis experiments corroborate its reasonable band gap, efficient charge separation and transfer, widened visible-light adsorption, easy solid-liquid separation, good stability and superior catalytic activity of CNGB. Three CNGB samples with different ratios of g-C3 N4 and BiFeO3 (CNGB-1, -2, -3 with 2:4, 3:3, and 4:2, respectively), though possessing different adsorption ability, eventually remove all Cr(VI) ions via photocatalysis within 90 min...

Metallic Ag deposited BiPO4 /BiOBr/BiFeO3 ternary nano-hetero-structures were rationally designed and synthesized by a simple precipitation-wet impregnation-photo deposition method. The plasmonic junction possesses an excellent wide spectrum photo-response and makes best use of BiPO4 which is otherwise a poor photocatalyst. Ag@BiPO4 /BiOBr/BiFeO3 showed superior photocatalytic activity for degradation of norfloxacin (NFN) under visible, ultra-violet, near-infra-red and natural solar light. Especially catalyst APBF-3 (0...