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Lead-free multiferroic composite ceramics of 0.7BaTiO3-0.3Ni0.7Zn0.3Fe2O4 (BT-NZF) were prepared by the solid-state combustion technique. The BT and NZF powders were calcined in the range of 1100 to 1200 °C for 4 h and 900 to 1100 °C for 2 h, respectively. Afterward, BT-NZF composite ceramics were sintered between 1100 and 1250 °C for 4 h. The effect of the firing temperature on the phase formation, microstructure, electrical, and magnetic properties of BT-NZF composite ceramics was investigated. X-ray diffraction of BT and NFZ powders showed the highest purity phase were prepared the calcination temperatures of 1100 and 1050 °C, respectively. The BT-NZF composite ceramics exhibited coexisting tetragonal perovskite and cubic spinel phases. The maximum density of 5.85 g/cm3 was obtained when sintering the composite ceramics at 1125 °C. The dielectric constant at room temperature increased with increased sintering temperature. The hysteresis loops showed leakage current in all samples. Ferromagnetic properties showed the highest Ms ∼ 24.56 emu/g measured under a magnetic field of 10,000 Oe from the sample sintered at 1150 °C. [ABSTRACT FROM AUTHOR]

The combination of two dielectric-magnetic components in the same composite has been shown to significantly improve the effectiveness of electromagnetic (EM) shielding and microwave absorption (MWA) because they have both a combination of high dielectric and magnetic losses and good impedance matching. The novel Bi1/2(Na0.8K0.2)1/2TiO3/Fe3O4 (BNKT/Fe3O4) composite has been successfully synthesized by a two-step method with wide effective absorption bandwidth (EAB = 16 GHz) in the high-frequency (2-18 GHz). It was evident that the MWA efficiency of the BNKT/Fe3O4 composite has been significantly improved compared with pure Bi1/2(Na0.8K0.2)1/2TiO3 or Fe3O4 materials. In addition, the BNKT/Fe3O4 composite could achieve reflection loss (RL = -39.41 dB, ~99.99% at 10.16 GHz) with a sample thickness optimal (d = 4.7 mm). This work shows that the novel BNKT/Fe3O4 composite has excellent MWA properties, all contributing to a potential candidate in the electromagnetic wave absorption and shielding fields. [ABSTRACT FROM AUTHOR]

Bismuth ferrite (BFO) has gathered recent research interest due to the wide opportunity to engineer its optical, magnetic, and ferroelectric properties by doping it with suitable elements. Doping in BFO largely influences the optical and ferroelectric properties for various applications. Pristine and co-doped with rare-earth (Pr) and transition-metal elements (Mn, Co, and Cr) bismuth ferrite were synthesized using the sol–gel technique. X-ray diffraction analysis has been employed to extract the structural parameters of synthesized samples. As revealed through SEM analysis, grain size decreases by incorporating dopants in BFO. A significant improvement was observed in doped BFO samples. A decrease in the optical bandgap of BFO, having values in the range of 2.23–1.59 eV, has been observed with doping, resulting in an improved photovoltaic and photocatalytic response of the samples. The power conversion efficiency for doped samples suggests an improvement in the photovoltaic properties compared to pure BFO (ɳ% ~ 0.0382–12.4). In addition, an enhancement in photocatalytic efficiency (ɳ% ~ 90.08 to 96.89) has been observed for doped samples. Obtained results suggest that co-doping of rare-earth and transition elements in bismuth ferrite is a promising approach with wide applications in ferroelectrics, photovoltaics, and photocatalysis. [ABSTRACT FROM AUTHOR]

The impact of partial substitution of erbium and transition metal (zirconium/yttrium/niobium) at bismuth and iron site on multiferroism and magnetoelectric coupling of BFO was studied. Three samples Bi0.95Er0.05Fe0.98X0.02O3 (where X = Nb/Zr/Y) were prepared by sol–gel method. The structural, morphological, and elemental aspects of the samples were scrutinized. The ferroelectric, magnetic, and magnetoelectric properties of the samples were recorded. The combined effect of erbium and zirconium offered better saturated ferroelectric loop with greater remnant polarization value (0.74 µC/cm2). On including erbium and zirconium inside bismuth ferrite, the magnetization of BFO got improved very much with remanence value (0.095 emu/g). The combination of erbium and zirconium has intensified the magneto electric behavior in the bismuth ferrite. Interestingly, zirconium inclusion inside the BFO system instead of niobium and yttrium has provoked all the multifunctional aspects uniformly. [ABSTRACT FROM AUTHOR]

This work investigates the structural, dielectric, ferroelectric and magnetoelectric coupling properties of (1−x) LiNbO3 − (x) La0.9Na0.1MnO3 with x = 0.1, 0.2, and 0.3 nanocomposites. The composite of ferroelectric material LiNbO3 (LNB) and magnetic material La0.9Na0.1MnO3 (LNMO) was synthesized by the conventional solid-state reaction method. The X-ray diffraction study confirms the formation of the perovskite samples. The crystalline sizes of the samples increased with an increase in x. The improved properties of these composites by the addition of LNMO were investigated through various analysis methods. The composite with x = 0.3 exhibits the highest enhanced values of dielectric permittivity (ε′) and a.c. conductivity with the lowest activation energy Ea = 1.41 eV. The highest magnetoelectric coupling property is also observed for this concentration. This material has wide application in sensors, data storage devices and in pyroelectric applications. [ABSTRACT FROM AUTHOR]

Variations in the multiferroic properties of BiFeO3 (BFO) powders were investigated with respect to the crystallite size and Gd-doping. Nanoscale BFO powders with an average particle size range of ~ 30–80 nm were synthesized by a solid-state reaction using microwave-assisted heat treatment with Bi(NO3)3·5H20, FeC2O4·2H2O and Gd(NO3)3·6H2O as source precursors supplying Bi, Fe, and Gd, respectively. These were heat-treated at temperatures ranging from 200 to 700 °C. The reaction led to the formation of crystallite powders with a particle size of a few tens of nanometers. It was confirmed that these samples had multiferroic properties at room temperature, and the value of Ms varied significantly from ferromagnetic to antiferromagnetic and vice versa with the size of the powders. In particular, ferromagnetic and ferroelectric features were observed when the size of the BFO powder was < ~ 30 nm (half of the spin-canted cycle). As the crystallite size was reduced to that corresponding to half of the spin canted cycle, the value of Ms increased by 8.8 times from 1.41 to 12.46 memu/g. Compared to pure BFO, when Gd was doped, Ms values increased by ~ 60% and 240% in ~ 30 nm and ~ 60 nm particle-sized powders. [ABSTRACT FROM AUTHOR]

A multiferroic material with a wide range of uses is bismuth ferrite, which shows outstanding potential. Ca and Ti co-doped BFO samples have been synthesized by the modified sol–gel method. The crystal structures of the samples have been confirmed by x-ray diffraction. The microscopic dielectric relaxations and conduction processes in these materials have been analyzed using complex impedance, complex electric modulus, and frequency-dependent ac conductivity analyses. The modified Debye's function has been used to study the dispersion behavior of the dielectric constant. The brick-layer model has been used to describe the dielectric characteristics of each sample. Furthermore, to study the conduction mechanism, ac conductivity data have been analyzed using Jonscher's power law and the Arrhenius equation. The Arrhenius technique was used to calculate the relaxation time as well as the activation energies using the imaginary part of the electrical impedance and the modulus. The presence of non-Debye-type relaxation processes, which include localized and long-range relaxation processes, is supported by the electric modulus spectroscopy. [ABSTRACT FROM AUTHOR]

Third order optical nonlinearity and multiferroicity of perovskite ZrFeO3 nanocrystalline thin films are investigated in this work. Rietveld refinement of XRD pattern of ZrFeO3 nanoparticles synthesized by sol-gel method confirmed the monoclinic structure with space group P2m. Thin films of ZrFeO3 nanoparticles were deposited on glass substrates by thermal evaporation method. Open aperture Z-scan technique with CW diode laser of 520 nm wavelength was used to investigate the nonlinear absorption coefficient (β) and imaginary part of third order nonlinear optical susceptibility (Im χ(3)) at 30 mW, 40 mW and 50 mW input laser powers. At each input power, ZrFeO3 thin film exhibits reverse saturation absorption (RSA) behavior with nonlinear absorption coefficient (β) of the order of 3.22 × 10−4 cm/W, which is found to decrease with an increase in power.ZrFeO3 thin film exhibited multiferroic properties with Mr = 0.0042 emu/g Hc = 0.326 kOe, Pr = 0.667 µC/cm2and Ec = 1.145 kV/cm. The results imply that ZrFeO3 films can be considered as a promising perovskite nanomaterial for future applications in multiferroic and nonlinear optical devices. Highlights: ZrFeO3 nanoparticles were synthesized by sol-gel method. ZrFeO3 nanocrystalline thin films were deposited on a glass substrate. ZrFeO3 thin films shows third order optical nonlinearity and multiferroic properties. Reverse Saturable absorption exhibited by ZrFeO3 Thin films at 520 nm. [ABSTRACT FROM AUTHOR]

With flexibility in tuning their electric and magnetic properties, multiferroics can be used in information exchange and storage in ways that are very different from the present electronic materials. Here we use resonant soft X-ray scattering spectroscopy to study the F-type (0,τ,0) and C-type (0, 1–2τ, 0) diffraction peaks from sinusoidal antiferromagnetic spin order in multiferroic DyMnO3. By comparing the temperature dependence of ordering wave vectors τ, peak intensities I, and correlation lengths λ measured at Mn L2-, O K-, and Dy M5-edges, we show that the nearly perfect locking between the ordering wave vectors from Dy 4f states and Mn 3d orbitals manifesting the second harmonic diffraction peak implies the notable orbital involvement in the coupling between Mn and Dy spins. Our DFT calculations further suggest that the lattice response to different antiferromagnetic ground states (A-type versus E-type) is much weaker in TbMnO3, in agreement with previous claim that the symmetric exchange interaction can be an important factor for understanding the ferroelectricity in DyMnO3 than in TbMnO3.

In the present work, we have synthesized rare-earth ion modified Bi4−xRExTi2Fe0.7Co0.3O12−δ (RE = Dy, Sm, La) multiferroic compounds by the conventional solid-state route. Analysis of X-ray diffraction by Rietveld refinement confirmed the formation of a polycrystalline orthorhombic phase. The morphological features revealed a non-uniform, randomly oriented, plate-like grain structure. The peaks evident in the Raman spectra closely corresponded to those of orthorhombic Aurivillius phases. Dielectric studies and impedance measurements were carried out. Asymmetric complex impedance spectra suggested the relaxation of charge carriers belonging to the non-Debye type and controlled by a thermally activated process. Temperature-dependent AC conductivity data showed a change of slope in the vicinity of the phase transition temperature of both magnetic and electrical coupling natures. Based on the universal law and its exponent nature, one can suppose that the conduction process is governed by a small polaron hopping mechanism but significant distortion of TiO6 octahedral. The doping of the A-sites with rare-earth element ions and changes in the concentrations of Fe and Co ions located on the B-sites manifested themselves in saturated magnetic hysteresis loops, indicating competitive interactions between ferroelectric and canted antiferromagnetic spins. The magnetic order in the samples is attributed to pair-wise interactions between adjacent Fe3+–O–Fe3+, Co2+/3+–O–Co3+/2+, and Co2+/3+–O–Fe3+ ions or Dzyaloshinskii–Moriya interactions among magnetic ions in the adjacent sub-lattices. As a result, enhanced magnetoelectric coefficients of 42.4 mV/cm-Oe, 30.3 mV/cm-Oe, and 21.6 mV/cm-Oe for Bi4−xDyxTi2Fe0.7Co0.3O12−δ (DBTFC), Bi4−xLaxTi2Fe0.7Co0.3O12−δ (LBTFC), and Bi4−xSmxTi2Fe0.7Co0.3O12−δ (SBTFC), respectively, have been obtained at lower magnetic fields (

The search for novel materials with enhanced characteristics for the advancement of flexible electronic devices and energy harvesting devices is currently a significant concern. Multiferroics are a prominent example of energy conversion materials. The magnetoelectric conversion in a flexible composite based on a piezopolymer layer and a magnetic elastomer layer was investigated. The study focused on investigating the dynamic magnetoelectric effect in various configurations of external alternating and constant homogeneous magnetic fields (L-T and T-T configurations). The T-T geometry exhibited a two orders of magnitude higher coefficient of the magnetoelectric effect compared to the L-T geometry. Mechanisms of structure bending in both geometries were proposed and discussed. A theory was put forward to explain the change in the resonance frequency in a uniform external field. A giant value of frequency tuning in a magnetic field of up to 362% was demonstrated; one of the highest values of the magnetoelectric effect yet recorded in polymer multiferroics was observed, reaching up to 134.3 V/(Oe∙cm).

In our studies, we combined two powdered materials, i.e., ferroelectric triglycine sulfate (TGS) and ferrimagnetic magnetite Fe3O4, to obtain a magnetoelectric composite. The ferroelectric (E) part, i.e., TGS, was a hybrid organic–inorganic crystal, which we obtained as a pure single crystal from an aqueous solution using a static water evaporation method. The magnetic (M) part of the composite was commercially available magnetite. The samples used for the dielectric and magnetoelectric measurements were cold-pressed and made in the form of a circular tablet. The measuring electrodes were made of silver-based conductive paste and were attached to the sample. We measured the temperature dependencies of selected electrical parameters (e.g., dielectric permittivity, electrical capacity, and loss angle tangent). We used the dynamic lock-in method to check whether magnetoelectric coupling existed between the E and M phases. In this paper, we present the dielectric properties of pure monocrystalline TGS as a reference sample and compare the results for TGS powder, TGS + carbon powder, and TGS + Fe3O4 powder. The magnetoelectric coupling presumably appeared for the composite TGS + 10 wt. % Fe3O4, as evidenced by the shift in the phase transition temperature in the TGS. Moreover, the theoretical interpretation of the effect is proposed.

Using rf cathode sputtering in an oxygen atmosphere, we produced a heterostructure based on the bismuth ferrite (BFO) multiferroic and barium strontium niobate (SBN) ferroelectric: BiFeO3(1000 nm)/Sr0.5Ba0.5Nb2O6(1000 nm)/Pt(001)/MgO(001). It was free of impurity phases and had a root mean square surface roughness within 1% of its thickness. All of the layers in the heterostructure were grown epitaxially. The SBN-50 layer consisted of orientation domains tilted in the plane of the interface by ±18.4° with respect to the MgO substrate axes, and the crystallographic axes of the BFO and Pt layers were parallel to the substrate axes. The ferroelectric polarization of the material at U = 90 V was shown to be 59.3 μC/cm2. Our results demonstrate that, to describe the behavior of the relative dielectric permittivity (ε) of the heterostructure in the range 25–250°C, it is sufficient to take into account the ε(t) data for each layer. The mechanisms underlying the observed effects are discussed. [ABSTRACT FROM AUTHOR]

The praseodymium Pr3+ doped at Bi site of Ba0.1Bi0.9(Ti0.9Zr0.1)0.1Fe0.9O3, under low concentrations (0%, 0.1%, 0.5% and 1% abbreviated as BBTZF0, Pr-BBTZF001, Pr-BBTZF005 and Pr-BBTZF01, respectively) were prepared by the solid-state reaction method. A detailed investigation has been made on structural, microstructural, ferroelectric and dielectric properties of Ba0.1(Bi1−xPrx)0.9(Ti0.9Zr0.1)0.1Fe0.9O3 ceramics. Rietveld refinement fitting revealed that the structure of these ceramics, at room temperature is rhombohedral with space group R3c. The cell volume decreased with increasing Pr-content due to the smaller ionic radius of the Pr. Temperature dependence of the dielectric constant (ε′r) of all prepared ceramics showed anomaly around TN (antiferromagnetic transition temperature); thus suggesting a magneto-electric coupling in these materials. The shift of TN with frequency is attributed to the Maxwell Wagner relaxation rather than the relaxor behavior. The P–E loop study shows the improved ferroelectric behavior and the reduced leakage current density with Pr doping. Moreover, the energy storage properties showed a clear enhancement upon the increase of the Pr concentration. The recoverable energy storage density (Wrec) of 2.75 J cm−3 with energy storage efficiency (η) of 44.52% was achieved for Pr-BBTZF01. [ABSTRACT FROM AUTHOR]

To investigate the effect of synthesis procedure and sintering temperature on the functional properties of perovskite/spinel ceramics, BaTiO3/CoFe2O4 composites were prepared by thermal decomposition, coprecipitation, and microemulsion method, and sintered at 1150°C and 1300°C. The phase composition and morphology of as-prepared powders as well as sintered ceramics were thoroughly examined by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS). The dielectric and ferroelectric measurements were performed in detail. Generally, the samples sintered at 1300°C had better performances than those sintered at 1150°C. The composite synthesized by thermal decomposition and sintered at 1300 °C stands out among other prepared BaTiO3/CoFe2O4 ceramics, owing to high stability in the wide frequency range and low leakage currents. The obtained results indicate that such composite might be successfully applied as a functional multiferroic. [ABSTRACT FROM AUTHOR]

Nanocrystalline particles of a bismuth ferrite (BiFO3, BFO) co-doped by praseodymium and cobalt, Bi1−xPrxFe1−xCoxO3 (x = 0.00, 0.02, 0.08), were synthesized using the modified sol–gel method in this study. X-ray diffraction (XRD) was used to assess the phase purity and crystallinity of the synthesized particles. The obtained XRD pattern matches perfectly with the standard Joint Committee on Powder Diffraction Standards (JCPDS) card number 71-2494. The synthesized nanoparticles maintain the rhombohedral symmetry in the R3c space group is also confirmed by XRD data. With several excitation wavelengths, to investigate the modes of vibration in doped nanoparticles, Raman scattering spectra for the wavelength range of around 532 nm were obtained. Doping enhances grain size, resulting in a large surface area for active sites, as seen by field emission scanning electron microscopy (FESEM) pictures. The spontaneous magnetization was found to be 0.278, 1.128 and 0.625 emu/g at an applied magnetic field of 30,000 G for praseodymium and cobalt doped BFO nanoparticles, (Bi1−xPrxFe1−xCoxO3 (x = 0.00, x = 0.02 and 0.08)). [ABSTRACT FROM AUTHOR]

Multiferroic materials with coexisting of at least two ferroic orders (ferromagnetic, ferroelectric, or ferroelastic) have recently attracted the interest of researchers due to their potential applications as multifunctional devices. Herein, we report the synthesis and detailed characterization of the multiferroic CoFe2O4–Ba0.95Ca0.05Ti0.89Sn0.11O3 core–shell nanofibers (CFO@BCTSn NFs) prepared by a sol–gel coaxial electrospinning technique. The scanning and transmission electron microscopes were used to check nanofibers' core–shell structure/configuration, with fiber diameters ranging from 150 to 250 nm. The X-ray diffraction analysis confirms the presence of both the spinel structure of the CFO and the perovskite structure of the BCTSn. Piezoresponse force microscopy and magnetic hysteresis were used to confirm the multiferroicity of CFO@BCTSn NFs. Notably, the maximum magnetization and remanent magnetization of NFs are found to be 11.63 emu g–1 and 1.43 emu g–1, respectively. Meanwhile, the maximum piezoelectric response d33eff is around 6 pm V–1. The magnetoelectric (ME) coefficient obtained for the CFO@BCTSn NFs is 346 mV cm–1 Oe–1 at the field of 10 kG. These findings may lead to development of nanoscale Pb-free magnetic field sensors and magnetoelectric device applications. [ABSTRACT FROM AUTHOR]

Different compositions of the nanocomposite lead-free multiferroic systems are fabricated by employing piezoelectric polyaniline (PANI) and magnetostrictive Ni0.5Co0.5Fe2O4 (NCF) by varying the NCF weight fraction. The current work reports the synthesis of xNCF:(1-x)PANI hybrid composite systems prepared via the physical blending method. X-ray powder diffraction (XRD) exhibits the presence of both; a polymeric amorphous phase of PANI (matrix) and a crystalline phase of inverse spinel ferrite NCF (filler) in the composites. The microstructure analysis along with the elemental composition of the samples are studied via Field emission scanning electron microscopy (FESEM) and Energy Dispersive X-ray Analysis (EDAX) respectively. Here, frequency-dependent dielectric permittivity exhibits percolation-type behavior where permittivity (ε′) attains a peak at a critical weight fraction (x = 0.3). The magnetic properties for the particular stoichiometric concentration (x = 0.3) of the composite exhibit a large enhancement in the saturation magnetization (Ms) of 75.22 emu g−1, while maintaining the soft ferromagnetism in the nanocomposite system. The switching behavior of electrical polarization in composite systems exhibits strong temperature dependence with a ferroelectric loop that appears to persist at even low temperatures (5 K). The remnant electrical polarization (Pr) is found to decrease with the increase in ferrite (NCF) concentration. Hence, the developed composite system at the high electric field exhibits both ferroelectric and ferromagnetic characteristics without significant conductive losses making it suitable for potential multiferroic and capacitor applications. [ABSTRACT FROM AUTHOR]

The phase composition, structure, and optical properties of the BiFeO3/SrTiO3/Al2O3 (c-cut) heterostructure have been studied using XRD analysis, spectrophotometry, and multi-angle ellipsometry. BFO/STO/A12O3 heterostructures have been obtained by high-frequency cathode sputtering in an oxygen atmosphere using the intermittent deposition technology. It was found that the BiFeO3 and SrTiO3 layers grew with an orientation in the direction of the [111] crystallographic axis parallel to the normal to the Al2O3 substrate. It has been shown that the damaged layer on the surface of the heterostructure does not exceed 2‒3 nm, and no signs of the presence of boundary layers at the Al2O3–SrTiO3 and SrTiO3–BiFeO3 interfaces have been identified. The dispersion dependences of the refractive indices of BFO and STO layers are calculated. The reasons for the revealed regularities are discussed. [ABSTRACT FROM AUTHOR]

Novel multiferroic nanoparticles Sm1−xHoxFeO3 have been prepared using a simple citrate auto-combustion method. According to the X-ray diffraction (XRD) data, the multiferroic samples had an orthorhombic single phase structure. The field emission scanning electron microscope (FESEM) illustrated that the nanoparticles possessed a cotton-like morphology with a porous nature. The vibrating sample magnetometer (VSM) demonstrates the antiferromagnetic (AFM) behavior of the samples. The maximum magnetization (Mm) of Sm0.95Ho0.05FeO3 is five times greater than that of SmFeO3. The ferroelectricity of Sm1−xHoxFeO3 has Г2-spin structure. The antiferromagnetic (AFM) spin canting has a great effect on both the magnetization and the ferroelectricity of the investigated perovskites. Sm1−xHoxFeO3; 0.0 ≤ x ≤ 0.10 samples are concluded to be novel single-phase multiferroic materials capable of adsorbing toxic chromium (Cr6+) metal ions from water. A hydrogen potential of pH 6 is the best condition for precipitating chromium ions. The adsorption of Cr6+ ions on Sm1−xHoxFeO3 was studied using the Langmuir and Freundlich isotherm models. [ABSTRACT FROM AUTHOR]

Nanocrystalline La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology were studied using X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning electron microscopy (SEM). Magnetic properties were studied using magnetometry methods and the valency changes of the cations after alkali ions doping were studied using X-ray photoelectron spectroscopy (XPS). The influence of the sintering pressure on the structural and magnetic properties of the manganites doped with different alkali ions and chromium was also investigated. Magnetization properties were studied as a function of sintering pressure and type of the dopant. Chemical doping with alkali ions as well as external pressure significantly changed the magnetic properties of the compounds. It was found that the magnetic properties of the manganites could be predictably modified through the use of a suitable dopant element. [ABSTRACT FROM AUTHOR]

BiFeO3 fibers were prepared by the Laser Floating Zone (LFZ) technique using different growth speeds. The structural characterization of the samples was undertaken using X-ray diffraction (XRD) and Raman spectroscopy, the morphological characterization by scanning electron microscopy (SEM), and the electrical characterization by impedance spectroscopy. The XRD patterns showed that BiFeO3 was the major phase in all the samples. Fibers grown at 10 mm/h showed more promising structural and morphological properties. The dielectric characterization revealed that all samples have at least one dielectric relaxation phenomenon that is thermally activated. It was also verified that the dielectric constant is higher at a growth pull rate speed of 10 mm/h. [ABSTRACT FROM AUTHOR]

A Mn and Cu co-doping BiFeO3 (BFO) thin film was fabricated on FTO/glass substrate by sol-gel method with a sequential layer deposition process. The raw materials using in the starting solution were bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O). Manganese (II) acetate tetrahydrate (C4H6MnO4·4H2O) and copper (II) acetate monohydrate ((Ch3COO)2Cu·H2O) were used as dopants. All of these previous reagents were mixed together using ethylene glycol (HOCH2CH2OH) as solvent. The atomic ratio used was BiFe0.94Mn0.04Cu0.02O3 (BFMCO) and 5 mol% of excess of bismuth was employed to compensate its volatility during high temperature annealing. The structural, morphological, optical properties and the charge transport mechanisms of the sample were studied using X-rays Diffraction (XRD), Scanning Electron Microscopy (SEM) and UV-visible spectroscopy, respectively. The chemical composition was studied by X-ray Photoelectron Spectroscopy (XPS). Simultaneously, a comparison was made between BFO and BFMCO thin films, prepared and characterized by the same experimental process, which allowed and knowing the effect of Cu and Mn co-doping on the structure and physical properties of BFO. [ABSTRACT FROM AUTHOR]

Multilayered magnetoelectric materials are of great interest for investigations due to their unique tuneable properties and giant values of magnetoelectric effect. The flexible layered structures consisting of soft components can reveal lower values of the resonant frequency for the dynamic magnetoelectric effect appearing in bending deformation mode. The double-layered structure based on the piezoelectric polymer polyvinylidene fluoride and a magnetoactive elastomer (MAE) with carbonyl iron particles in a cantilever configuration was investigated in this work. The gradient AC magnetic field was applied to the structure, causing the bending of the sample due to the attraction acting on the magnetic component. The resonant enhancement of the magnetoelectric effect was observed. The main resonant frequency for the samples depended on the MAE properties, namely, their thickness and concentration of iron particles, and was 156–163 Hz for a 0.3 mm MAE layer and 50–72 Hz for a 3 mm MAE layer; the resonant frequency depended on bias DC magnetic field as well. The results obtained can extend the application area of these devices for energy harvesting. [ABSTRACT FROM AUTHOR]

In this communication, we report the results of studies on the effect of Ba and Ti co-doping on the structural, electrical, transport and magnetic properties of nanostructured LaFeO3 films grown on conducting LaNiO3 (LNO) buffer layer deposited on LaAlO3 (LAO) substrate. The structural property investigations on (La1-xBax)(Fe1-xTix)O3 (LBFT); x = 0.0–0.5 films, carried out using X-ray diffraction measurements, revealed the single phasic behaviour of all the films with the compressive strain varying with the doping. Surface morphology studied using atomic force microscopy, show the presence of fine granular surface roughness < 1 nm while the interface grain morphology study using cross-sectional SEM study, reveal the grain mixing of LNO and LBFT layers at the interface region. Modifications in the dielectric behaviour of LBFT/LNO heterostructure with Ba and Ti co-doping have been discussed in light of the hopping of charge carriers and interface mixing at LBFT/LNO layers. Observation of partially saturated ferroelectric loop in films doped with higher concentrations of Ba and Ti, may be attributed to the formation of non-centrosymmetric structure. In addition, the magnetization measurements on the Ba and Ti co-doped LBFT films depict the doping concentration dependent magnetic behaviour. [ABSTRACT FROM AUTHOR]

The magnetoelectric properties of exchange-coupled Ni/CoFeB-based composite multiferroic microstructures are investigated. The strength and sign of the magnetoelastic effect are found to be strongly correlated with the ratio between the thicknesses of two magnetostrictive materials. In cases where the thickness ratio deviates significantly from one, the magnetoelastic behavior of the multiferroic microstructures is dominated by the thicker layer, which contributes more strongly to the observed magnetoelastic effect. More symmetric structures with a thickness ratio equal to one show an emergent interfacial behavior which cannot be accounted for simply by summing up the magnetoelastic effects occurring in the two constituent layers. This aspect is clearly visible in the case of ultrathin bilayers, where the exchange coupling drastically affects the magnetic behavior of the Ni layer, making the Ni/CoFeB bilayer a promising next-generation synthetic magnetic system entirely. This study demonstrates the richness and high tunability of composite multiferroic systems based on coupled magnetic bilayers compared to their single magnetic layer counterparts. Furthermore, because of the compatibility of CoFeB with present magnetic tunnel junction-based spintronic technologies, the reported findings are expected to be of great interest for the development of ultralow-power magnetoelectric memory devices.

The paper presents the results of a study of the influence of a constant magnetic field on the dispersion of the complex permittivity of a layered composite (connectivity 2-2) based on barium titanate – barium ferrite. It is shown that in the manufacture of a magnetoelectric composite of barium titanate – barium ferrite with a connectivity of 2-2, a strong diffusion of iron appears into the barium titanate ceramic layer at the interface between the two materials. It was found that iron penetrates evenly, with random deviations, and no exponential decline as iron enters into barium titanate is observed. It has been established that a constant magnetic field does not affect the dielectric characteristics in an alternating electric field at frequencies above 1600 Hz. At lower frequencies, annealing in the paraelectric phase increases the resistance of the sample, and subsequent exposure to a constant magnetic field leads to its decrease. It was revealed that changing the type of connectivity of the magnetoelectric composite from 0-3 to 2-2 adds additional, smaller, resonance and antiresonance peaks in the study of piezoelectric properties by the resonance-antiresonance method. At the same time, the samples have sufficient values of the piezoelectric modulus for practical application (d31 > 40·10-12 C/N; d33 > 120·10-12 C/N).

Over recent decades, the scientific community has managed to make great progress in the theoretical investigation and practical characterization of bismuth ferrite thin films. However, there is still much work to be completed in the field of magnetic property analysis. Under a normal operational temperature, the ferroelectric properties of bismuth ferrite could overcome the magnetic properties due to the robustness of ferroelectric alignment. Therefore, investigation of the ferroelectric domain structure is crucial for functionality of any potential devices. This paper reports deposition and analyzation of bismuth ferrite thin films by Piezoresponse Force Microscopy (PFM) and XPS methods, aiming to provide a characterization of deposited thin films. In this paper, thin films of 100 nm thick bismuth ferrite material were prepared by pulsed laser deposition on multilayer substrates Pt/Ti(TiO2)/Si. Our main purpose for the PFM investigation in this paper is to determine which magnetic pattern will be observed on Pt/Ti/Si and Pt/TiO2/Si multilayer substrates under certain deposition parameters by utilizing the PLD method and using samples of a deposited thickness of 100 nm. It was also important to determine how strong the measured piezoelectric response will be, considering parameters mentioned previously. By establishing a clear understanding of how prepared thin films react on various biases, we have provided a foundation for future research involving the formation of piezoelectric grains, thickness-dependent domain wall formations, and the effect of the substrate topology on the magnetic properties of bismuth ferrite films. [ABSTRACT FROM AUTHOR]

This study reports on the structure, electric, and magnetic properties of Bi0.5(Na0.80,K0.20)0.5TiO3/BaZrO3 (BNKT/BZO) heterolayered films synthesized via chemical solution deposition on Pt/Ti/SiO2/Si substrates. The influence of different heterolayered configurations on the microstructure, electric and magnetic properties of the films was investigated thoroughly. The heterostructures are expected to generate strongly correlated electron systems in the BNKT and BZO layers that cause a magnetic interface effect in the BNKT/BZO conjunction layer. The BZO layer also prevents metal ion evaporation, resulting in a decline in oxygen vacancies and an enhancement in the electric and magnetic properties. The obtained results show that magnetic properties and leakage current density (J) of BNKT/BZO heterolayered films were greatly improved thanks to the heterolayered structure. Heterolayered 4BNKT/2BZO films (M42) yield the highest M s and M r values of 14.4 emu cm−3 and 1.7 emu cm−3, respectively, about three times higher than multilayered BNKT. Thanks to heterolayered structure, J decreases strongly from 16.0 × 10−4 A cm−2 for BNKT films to 1.4 × 10−4 A cm−2 for heterolayered M42 films. It has been verified that the leakage current in BNKT/BZO heterolayered films follows the Schottky barrier mechanism, with the barrier height fluctuating between 0.80 eV and 0.92 eV. The results of the study show that BNKT/BZO heterolayered films may be suitable for use in environmentally friendly multifunction devices. [ABSTRACT FROM AUTHOR]

The full E-field control of multiferroic interfacial magnetism is a long-standing challenge for micro-electromechanical systems (MEMS) and has the potential to transform electronics operation mechanisms. When scaling down conventional complementary metal-oxide semiconductor (CMOS) devices, increased heating dissipation becomes a top concern. Combining the highly correlated ferroic orders, notably the strongly coupled interfacial magnetoelectric (ME) interactions, may lead to devices beyond CMOS. These devices use the electric field to regulate magnetization, which opens up the prospect of downsizing, improved performance, and lower power consumption. To broadly survey this tremendous scope within the last five years, this review summarizes advances in voltage control of interfacial magnetism (VCIM) with various material system selection; controlling effects with different gating methods are also explored. Five classic mechanisms are demonstrated: strain, exchange bias, orbital reconstruction, and the electrostatic and electrochemical. The encouraging photovoltaic approach is also discussed. Each method's capabilities and application scenarios are compared. Analyses of the comprehensive gating results of different magnetic coupling effects such as perpendicular magnetic anisotropy (PMA) and Ruderman—Kittel—Kasuya—Yosida (RKKY) are additionally made. At last, controlling of skyrmions and two-dimensional (2D) material magnetization is summarized, indicating that E-field gating offers a universal approach with few limitations for material selection. These results point to potential for E-field control interfacial magnetism and predict significant future advancements for spintronics. [ABSTRACT FROM AUTHOR]

In the frequency range of 3.2–12 GHz, the microwave energy absorption spectra of a series of the (1-x)BiFeO3 – xLaMnO3 solid solutions with a concentration of x = 0.1 − 0.9 were studied. The spectra contain the absorption maxima of the resonant type, the magnitudes, resonant frequencies, and number of which depend on the x concentration and temperature. At different heights from the surface of the samples under study, located on the microstrip line, the emission spectra of the electric and magnetic components of the microwave field were obtained. The X-ray diffraction data and the obtained absorption and emission spectra are interconnected and complement each other. The features of the spectra are discussed from the point of view of the contribution to the emission and absorption of the energy of the dielectric walls of the twins resonating in the electromagnetic field. The features of the magnetic moments of multiferroics are also discussed. [ABSTRACT FROM AUTHOR]

In this work, we have prepared intergrowth of multiferroic compounds namely Bi4RTi3Fe0.7Co0.3O15-Bi3RTi2Fe0.7Co0.3O12−δ (BRTFCO15-BRTFCO12) (rare earth (R) = Dy, Sm, La) by solid-state reaction method. From the X-ray diffraction Rietveld refinement, the structure of the intergrowths was found to be orthorhombic in which satisfactory fittings establish the existence of three-layered (space group: b 2 c b) and four-layered compounds (space group: A21am). Analysis of magnetic measurements confirmed a larger magnetization for theSm-modified intergrowth compound (BSTFCO15-BSTFCO12) compared to Dy- and La-doped ones. The emergence of higher magnetic properties can be due to distortion in the unit cell when some Bi3+ ions are replaced with the Sm3+, bonding of Fe3+-O-Co3+ as well as a possible mixture of FexCoy-type nanoparticles that are formed generally in the synthesis of intergrowths. The changes in the magnetic state of the Aurivillius intergrowths have been reflected in the magnetoelectric (ME) coupling: higher ME coefficient (~30 mV/Cm-Oe) at lower magnetic fields and is constant up to 3 kOe. The results were corroborated by Raman spectroscopy and variation of temperature with magnetization data. The results revealed that the RE-modified intergrowth route is an effective preparative method for higher-layer Aurivillius multiferroic ceramics. [ABSTRACT FROM AUTHOR]

Studies of the dielectric and ferroelectric properties of c-oriented Ba2NdFeNb4O15 films is carried out at T = −190...200 °C using dielectric spectroscopy methods and ferroelectric hysteresis loops analysis. The films were obtained by RF-cathode sputtering method in an oxygen atmosphere. The PA-FE phase transition region, the features of the dielectric response formation, and the mechanisms responsible for that formation are revealed in the material. It is shown that the studied materials are characterized by high values of energy efficiency parameters. The reasons of the revealed regularities and the prospects of the use of these materials are discussed. [ABSTRACT FROM AUTHOR]

After the discovery of bulk photovoltaic effect more than half a century ago, ferro-electrical and magneto-optical experiments have provided insights into various related topics, revealing above bandgap open voltages and non-central symmetrical current mechanisms. However, the nature of the photon-generated carriers responses and their microscopic mechanisms remain unclear. Here, all-inorganic perovskite Bi 0.85 Gd 0.15 Fe 1 − x Mn x O 3 thin films were prepared by a sol-gel process and the effects of Gd and Mn co-doped bismuth ferrites on their microtopography, grain boundries, multiferroic, and optical properties were studied. We discovered a simple "proof of principle" type new method that by one-step measuring the leakage current, one can demonstrate the value of photo generated current being the sum of ballistic current and shift current, which are combined to form the so-called bulk photovoltaic current, and can be related to the prototype intrinsic properties such as magneto-optical coupling and ferroelectric polarization. This result has significant potential influence on design principles for engineering multiferroic optoelectronic devices and future photovoltaic industry development. [ABSTRACT FROM AUTHOR]

The import marvel in multiferroic substances is the existence of spontaneous polarization and magnetization which enable these materials meet the needs of technological applications. Multiferroic of BiFeO3 and nickel-doped magnetite was synthesized separately by flash and co-precipitation methods, respectively. The two phases were confirmed by X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transformed infrared (FTIR) analysis. The dielectric properties of BiFeO3/Ni0.1Fe2.9O4 nanocomposite were studied as a function of temperature as well as frequency. Based on the frequency dependent of ac conductivity results, it indicated that the conduction occurs through tunneling and small polaron hopping. The composite sample shows excellent results for heavy metal (Cr6+) removal from wastewater as the removal efficiency was reached to 75% at PH 6 after 40 min. The adsorption of Cr (VI) on the surface of nanocomposite was occurred through Langmuir isotherm and follows pseudo-second-order kinetics. The goal and novelty of this work were to investigate the structural, morphological and dielectric as well as magnetic properties of multiferroic nanocomposite material (BiFeO3/Ni0.1Fe2.9O4) and test its efficiency for heavy metal removal. [ABSTRACT FROM AUTHOR]

The geometry–dependent magnetoelectric (ME) and exchange bias (EB) effects of the nano ME sensor were investigated. The sensor consisted of the Longitudinal–Transverse (L–T) mode bi–layer bar structure comprising the ferromagnetic (FM) and ferroelectric (FE) materials and the anti–ferromagnetic (AFM) material. The bi–layer ME coefficient was derived from constitutive equations and Newton's second law. The trade–off between peak ME coefficient and optimal thickness ratio was realized. At the frequency × structure length = 0.1 and 1200, minimum and maximum peak ME coefficients of the Terfenol–D/PZT bi-layer were around 1756 and 5617 mV/Oe·cm, respectively, with 0.43 and 0.19 optimal thickness ratios, respectively. Unfortunately, the bi-layer could not distinguish the opposite magnetic field directions due to their similar output voltages. PtMn and Cr2O3, the AFM, were introduced to produce the EB effect. The simulation results showed the exchange field starting at a minimum PtMn thickness of 6 nm. Nevertheless, Cr2O3 did not induce the exchange field due to its low anisotropy constant. The tri–layer ME sensor consisting of PZT (4.22 nm)/Terfenol–D (18 nm)/PtMn (6 nm) was demonstrated in sensing 2 Tbit/in2 magnetic bits. The average exchange field of 5100 Oe produced the output voltage difference of 12.96 mV, sufficient for most nanoscale magnetic sensing applications. [ABSTRACT FROM AUTHOR]

Materials exhibiting magnetoelectric effects have drawn great interest because of their intriguing physical phenomena and potential applications in electronic devices. The magnetoelectric (ME) coupling makes the materials promising for use in multifunctional devices with electric-field-tunable magnetism and magnetic-field-controlled ferroelectricity. Very recently, a strong ME effect has been found in the BaRFeO4 system (R is a rare-earth element), in which the ferroelectricity is driven by the onset of a long-range cycloidal antiferromagnetic order of Fe spins. However, previous studies have shown how complicated the synthesis procedure is to obtain single-phase samples of the materials. In this work, we present a simple and easy fabrication process to synthesise high-quality BaDyFeO4 using the conventional solid-state reaction method. The structural, morphological, and optical properties of the synthesised sample were investigated by means of X-ray diffraction, scanning electron microscopy, and UV-Vis spectroscopy, respectively. The sample was formed from high-quality microparticles. The X-ray diffraction study reveals the single-phase nature of the sample adopting the Pnma orthorhombic structure without any impurity phases. The detailed structural parameters were refined with Rietveld refinement. The sample demonstrates a direct gap semiconducting behaviour. The experimental results of the structural and electronic properties of BaDyFeO4 are complemented by density functional theory (DFT) calculations.

A facile sol–gel approach was utilized to synthesis BiFe _1-x Ti _x O _3 multiferroic ferrites, denoted as BFO- x Ti (with x from 0.00 to 0.10). XRD analysis revealed that the undoped BFO ferrite exhibited a rhombohedral structure, and a transition from the rhombohedral phase to the pseudo-cubic phase occurred as the Ti content increased. The optical band gap increased from 2.00 eV to 2.23 eV with a Ti substitution at 0.10 mol. The magnetic properties exhibited a transition from antiferromagnetic to ferromagnetic phase due to the structural phase transition and super-exchange interaction between the 3d orbitals of Ti ^4+ and Fe ^3+ /Fe ^2+ at the B-sites through oxygen vacacies. The sample with a 0.10 mol Ti substitution demonstrated the highest M _s and M _r values of 3.68 emu g ^−1 and 7.21 × 10 ^–3 emu g ^−1 , respectively. Overall, the results suggest that the BiFe _1-x Ti _x O _3 multiferroic ferrites with optimal composition hold promise for use in magneto-optical devices.

We report the magnetic-field-assisted electric-field-controlled domain switching of a magnetic single domain in a multiferroic/magnetoelectric Ni nanochevrons/[Pb(Mg1/3Nb2/3)O3]0.68–[PbTiO3]0.32 (PMN–PT) layered structure. Initially, a magnetic field was applied in the transverse direction across single-domain Ni nanochevrons to transform each of them into a two-domain state. Subsequently, an electric field was applied to the layered structure, exerting the converse magnetoelectric effect to transform/release the two-domain Ni nanochevrons into one of two possible single-domain states. Finally, the experimental results showed that approximately 50% of the single-domain Ni nanochevrons were switched permanently after applying our approach (i.e., the magnetization direction was permanently rotated by 180 degrees). These results mark important advancements for future nanoelectromagnetic systems.

The possibility of controlling physical properties via chemical doping is particularly important when considering the formation of both electrical and magnetic orderings in the same compounds, which are commonly referred as multiferroics [...]