Search

Abstract Ferro‐rotational (FR) materials, renowned for their distinctive material functionalities, present challenges in the growth of homo‐FR crystals (i.e., single FR domain). This study explores a cost‐effective approach to growing homo‐FR helimagnetic RbFe(SO4)2 (RFSO) crystals by lowering the crystal growth temperature below the TFR threshold using the high‐pressure hydrothermal method. Through polarized neutron diffraction experiments, it is observed that nearly 86% of RFSO crystals consist of a homo‐FR domain. Notably, RFSO displays remarkable stability in the FR phase, with an exceptionally high TFR of ≈573 K. Furthermore, RFSO exhibits a chiral helical magnetic structure with switchable ferroelectric polarization below 4 K. Importantly, external electric fields can induce a single magnetic domain state and manipulate its magnetic chirality. The findings suggest that the search for new FR magnets with outstanding material properties should consider magnetic sulfates as promising candidates.

This work successfully synthesized single-phase Aurivillius Bi4Ti2.75(FeNb)0.125O12 using a molten salt method and the natural precursor of Fe3+ ions extracted from Padang Beach sand. The study extensively examined the phase formation, crystal structure, grain morphology, and physical properties. X-ray diffraction (XRD) analysis combined with the Rietveld refinement technique confirms that Bi4Ti2.75(FeNb)0.125O12 adopts a B2cb orthorhombic structure. The refined atomic positions reveal that Bi3+ ions are located in the A-site within both the bismuth and perovskite layers, while the B-sites within the perovskite layers are primarily occupied by Ti4+/Nb5+/Fe3+ ions. The lower distortion of the inner B(1)O6 octahedra suggests the preference of Fe-rich clusters. The magnetization hysteresis suggests that the Bi4Ti2.75(FeNb)0.125O12 phase exhibits a weak antiferromagnetic state arising from the local short-range Fe–O–Fe antiferromagnetic ordering in the inner B(1)O6 octahedra. The electrical measurements reveal that the existence of ferroelectric ordering at room temperature comes from the structural distortion and the off-center ionic displacement. The energy storage capacity of 10.15 mJ/cm3 and efficiency (η) of 50.2% were obtained in ceramic sample under an electric field of 70 kV/cm at room temperature.

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.

This review reports the latest trends in the ceramic composite matrix used for the magnetoelectric (ME) effect. In the last few years, ME composite has become the center of attraction for use in various electrically and magnetically coupled devices. The growth and use of electronic components everywhere have propulsively accelerated the exploration of self-powered electronic and sensor network devices. ME is a feasible technique for addressing difficulties of traditional batteries such as short life span and frequent recharge difficulties. Self-charging multiferroic components have been found for the constant working of mobile electronics that use multiferroic composites in response to magnetoelectric energy transformation. Researchers have rigorously studied the rigid and flexible magnetoelectric composites for their suitability in applications. This paper gives a comparative study between rigid and flexible magnetoelectric composites based on their properties and provides knowledge about the materials for such types of composites. It reviews the latest polymer-based ME materials as well as the related fabrication and polarization methods. The review finally encapsulates the applications in biomedicine, ranging from mechanical energy harvesters to sensors and actuators.

Bi0.8Ba0.1Er0.1Fe0.96Cr0.02Mn0.02O3 (BBEFCMO) multiferroic ceramic was synthesized through the sol-gel route. The impact of incorporating various dopants into both A and B sites of the BiFeO3 was investigated, and structural, Raman, dielectric, electric, and magnetic properties were studied. X-ray diffraction analysis and Raman spectroscopy revealed a rhombohedral structure with the R3c space group for the doped material (BBEFCMO). Dielectric properties were examined across a frequency range of 102–106 Hz. The present multiferroic material exhibits a colossal dielectric constant and minimal dielectric loss tangent, making it suitable for applications in energy storage. Furthermore, the Cole-Cole type of relaxation was deduced from the imaginary part of the modulus for both grain and boundary-grain contributions. Overall, this study indicates that substituting ions in both A and B sites of BiFeO3 significantly enhances its multiferroic properties, as evidenced by dielectric and magnetic measurements.

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.

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.

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).

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 [...]

Neodymium doped Bismuth Iron Oxide (NdBiFeO3 - NBFO) with the composition Bi1-xNdxFeO3 (x = 0.02, 0.04&0.06) has been synthesized by microwave assisted combustion method. The properties of Neodymium (Nd3+) doped BFO nanoparticles were studied using various analytical techniques. The X-ray diffraction revealed the Rhombohedra phase formation of doped samples and decrease in crystallites size with increase in dopant concentration. The Fourier transform infrared spectroscopy confirms the presence of molecular vibration. Optical properties were studied using the UV data and optical band gaps of NBFO were calculated. The direct band gap of the materials is found to be 1.02eV, 1.78eV and 1.89eV for. The magnetic properties are studied using M-H graphs obtained from the Vibrational Sample Magnetometer. The M-H hysteresis loop shows decreased saturation magnetization (MS) and coercivity (HC) but increased remnant magnetization (M r) on substitution. The dielectric properties of doped samples were investigated using broad band dielectric spectrometer in the frequency range of 10 Hz to 10 MHz at room temperature.

In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe3O4, and a mixture of BaTiO3 (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films’ structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe3O4 system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies.

Two-dimensional multiferroic (2D) materials have garnered significant attention due to their potential in high-density, low-power multistate storage and spintronics applications. MXenes, a class of 2D transition metal carbides and nitrides, were first discovered in 2011, and have become the focus of research in various disciplines. Our study, utilizing first-principles calculations, examines the lattice structures, and electronic and magnetic properties of nitride MXenes with intrinsic band gaps, including V2NF2, V2NO2, Cr2NF2, Mo2NO2, Mo2NF2, and Mn2NO2. These nitride MXenes exhibit orbital ordering, and in some cases the orbital ordering induces magnetoelastic coupling or magnetoelectric coupling. Most notably, Cr2NF2 is a ferroelastic material with a spiral magnetic ordered phase, and the spiral magnetization propagation vector is coupled with the direction of ferroelastic strain. The ferroelectric phase can exist as an excited state in V2NO2, Cr2NF2, and Mo2NF2, with their magnetic order being coupled with polar displacements through orbital ordering. Our results also suggest that similar magnetoelectric coupling effects persist in the Janus MXenes V8N4O7F, Cr8N4F7O, and Mo8N4F7O. Remarkably, different phases of Mo8N4F7O, characterized by orbital ordering rearrangements, can be switched by applying external strain or an external electric field. Overall, our theoretical findings suggest that nitride MXenes hold promise as 2D multiferroic materials.

This article proposes a novel magnetoelectric (ME) effect-based ternary content addressable memory (TCAM). The potential array-level write and search performances of the proposed ME-TCAM are studied using experimentally calibrated compact physical models and SPICE simulations. The voltage-controlled operation of the ME devices eliminates the large joule heating present in the current-controlled magnetic devices and their low-voltage write operation makes them more energy-efficient compared to static random access memory-based TCAMs (SRAM-TCAMs). The proposed compact TCAM outperforms its SRAM counterpart with $1.35\times $ and $14.4\times $ improvements in search and write energy, respectively, and its nonvolatility eliminates the standby leakage. We project an error rate below $10^{-4}$ while considering various sources of variation in magnetic and CMOS devices. At the application level, using memory-augmented neural networks (MANNs), we project a $2\times $ energy-delay–area-product (EDAP) improvement over an SRAM-TCAM.

The article represents the results of studying of the influence of atom species in the perovskite multiferroic yttrium orthoferrite YFeO3 on magnetic configurations by ab-initio methods. Four magnetic configurations possible in magnetic sublattice that were formed by iron atoms were analyzed. It is shown that different magnetic orderings change the lattice parameters and the ions occupied positions while preserving symmetry of the unit cell, the lowest state responds G-AFM type magnetic ordering. The lattice parameters are in good relevant published experimental data. The atom species energy dependence shows that the main role in magnetic properties goes to iron and oxygen. In the ground state, magnetic properties relate with Dzyaloshinskii – Moriya interaction, while in other configurations, these relate with superexchange through Fe- O-Fe chains. Obtained results are useful for analyzing and designing straintronics devices. Also, the results can be interesting for interpretation and predicting magnetic properties of partially or fully substituted orthoferrites including substitution on rare-earth elements.

BiFeO3 (BFO) is extensively studied multiferroic material that possible to be integrated in next generation spintronics device. In this present research, BFO has been epitaxially grown on SrTiO3 (STO) substrates having various crystal orientations; (100), (110), and (111). We found that the lattice matching hold a pivotal factor in the epitaxial stabilization of BFO thin film. We also found that the magnetic properties of BFO thin film having various crystal orientations at below room temperature are different due to several reason, such as strain effect and crystal orientations.

It is shown in the work that as a result of sintering of composite samples of barium titanate (80 vol. %) – barium ferrite (20 vol. %) in a porcelain crucible at a temperature of 1300°C, a eutectic appears. As a result of comparing the properties of the samples obtained at different sintering temperatures, it was found that the samples sintered at 1250°C have optimal properties. The structure and dielectric properties of barium titanate ceramic samples and barium titanate (80 vol. %) – barium ferrite (20 vol. %) composite sintered at a temperature of 1250°C are compared. It has been shown that the addition of 20% barium ferrite to the composition of barium titanate increases the dielectric constant, pyroelectric coefficient, and piezoelectric modulus d33 of the composite of 1,5-2 times compared to barium titanate ceramics, while the value of the piezoelectric modulus d31 remains unchanged. The introduction of 20% barium ferrite into the barium titanate ceramics is sufficient for the resulting composite to have magnetic characteristics corresponding to pure barium ferrite.

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.

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.

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.

In this work, we investigate the influence of electric fields (E-fields) on the room-temperature magnetotransport behavior of an artificial multiferroic heterostructure, a Conetic alloy (Ni77Fe14Cu5Mo4) thin film/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (011). When the external magnetic field is parallel to the applied current, the switching field increases from 0.8 to 3.3 Oe at 0 and 8 kV/cm, respectively, and the corresponding magnetoresistance (MR) ratio at 20 Oe respectively decreases from 0.14% to 0.03% at 0 and 8 kV/cm. However, when the external magnetic field is perpendicular to the current, the switching field decreases from 10.1 to 1.7 Oe at 0 and 8 kV/cm, and the MR ratio in such a case decreases from −0.001% to −0.10%, respectively. Consequently, under the parallel and perpendicular modes, the tunabilities of the switching field are approximately +313% and −83%, and the MR ratio tunabilities under E-fields are approximately −79% and +9,900%, respectively. Such a large and anisotropic tunability of both the switching field and MR ratio is attributed to the ultrasoft magnetic property of the Conetic alloy thin film and anisotropic in-plane strain-mediated magnetoelectric coupling. However, the anisotropic MR ratio is approximately 0.15% and does not vary with the applied E-fields owing to the intrinsic property of Conetic thin films using transfer and circle transfer curve measurements, rather than the magnetization rotation caused by E-field-induced magnetoelastic anisotropy. This work demonstrates that multiferroic heterostructures with electrically tunable MR show considerable potential in designing energy-efficient electronic and spintronic devices.

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.

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.

Solid-state reaction between BaTiO3 and Fe2O3 was used to produce a multiferroic heterostructure composite. Commercial BaTiO3 and Fe(NO3)3•9H2O were suspended in ethanol for 30 minutes in an ultrasound bath. The prepared mixture was thermally processed at 300°C for 6 h. Sintering at 1300°C for 1 h resulted in a mixture of different phases, BaTiO3, BaFe12O19 and Ba12Ti28Fe15O84, which were confirmed by x-ray powder diffraction. A dense microstructure with a small volume fraction of closed porosity was indicated by the scanning electron microscopy, while a homogeneous distribution of Fe ions over BaTiO3 phase was visible from energy dispersive spectroscopy mapping. Doping of BaTiO3 with Fe2O3 resulted in formation of magnetic hexaferrite phases, as confirmed by dielectric measurements that showed a broadened maximum of the permittivity measured as a function of temperature.

xBiFeO3-(1-x)Ba5TbTi3V7O30 (xBFO-BTTV) ceramic composites with different x values were prepared by high temperature solid state reaction technique and sintering at 1073K. The formation of composite structure consisting of BFO and BTTV phases was confirmed by XRD study. Surface morphology was studied by scanning electron microscope (SEM) and shows that structure with high density was obtained in the composite 0.3BFOBTTV whereas the average grain size increases by increasing x, i.e. by increasing amount of BiFeO3 in the system. Magnetic measurements were done in a wide temperature range, i.e. from 10 to 350K, by vibrating sample magnetometer (VSM) and showed that the magnetization changes by changing the value of x in the composite. BiFeO3 is antiferromagnetic in nature with weak ferromagnetism. Addition of Ba5TbTi3V7O30 enhances magnetic properties of the composite and maximal coercivity and remnant magnetization are obtained in the composite 0.7BFO-BTTV.

Effect of starting Fe precursor (Fe2O3 and Fe3O4) on the multiferroic properties of BST (Ba0.96Sr0.04Ti0.91Fe0.09O3) ceramics has been investigated. Considerable changes in the ferroelectric and magnetic properties of these ceramics were observed. High crystallinity, tetragonal structure and phase purity of both the samples were confirmed using X-ray diffraction analysis. The field emission scanning electron microscopy analysis confirmed the uniform grain growth in both the samples with an average grain size of ≈0.40 μm. X-ray photoelectron spectroscopy analysis confirmed the presence of Fe2+ only and both Fe2+ and Fe3+ in Fe2O3- and Fe3O4-doped samples. The Fe3O4-doped BST samples displayed higher Pr and Mr values (2.32 μC/cm2and 0.012 emu/g) as compared to Fe2O3-doped BST samples. The M-E coupling response (≈10.56%) too was observed to be more pronounced in Fe3O4-doped BST samples. Our research work suggests that Fe3O4 doping in BST is better suited for multiferroic applications due to the presence of multivalent Fe ions.

A conventional solid-state method was used to prepare Pb(Fe1/3Ti1/3W1/3)O3 single perovskite material. The sample sintered at 900 °C was studied by XRD and after Rietveld refinement the orthorhombic structure with Pbam space group was confirmed. The FTIR frequency bands corresponding to Pb–O, Ti–O, O-lattice, W–O–W and Fe–O stretching vibrations together with the XRD data also confirmed that Fe2+ and W6+ ions are incorporated in the structure and most probably substituted Ti4+ ions at the B site of the perovskite ABO3 structure. The average grain size of the perovskite ceramics, estimated from SEM micrograph, was 1 to 2 µm. Variation of dielectric properties and AC conductivity with frequency and temperature revealed that the material had semiconducting nature and negative temperature coefficient of resistance (NTCR). The Nyquist plots were modelled with an equivalent circuit consisted of parallel capacitance, resistance and constant phase element corresponding to the grains (bulk) and grain boundaries. It was observed that grain resistance (Rb) of the sample decreases with the rise of temperature, which supports the NTCR behaviour. The semi-circular arcs of the Nyquist and Cole-Cole plots confirm the semiconducting nature of the sample.

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.

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 Bi0.85Gd0.15Fe1−xMnxO3 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.

Bismuth ferrite (BiFeO3) particles are prepared by a combined mechanochemical−thermal processing of a Bi2O3 + α-Fe2O3 mixture. Structural, magnetic, hyperfine, morphological and chemical properties of the as-prepared BiFeO3 are studied using X-ray diffraction (Rietveld refinement), 57Fe Mössbauer spectroscopy, SQUID magnetometry, electron microscopy and energy dispersive X-ray spectroscopy. It is revealed that the structure of the ferrite exhibits the long-range distortion (significantly tilted FeO6 octahedra) and the short-range disorder (deformed FeO6 octahedra). Consequently, these structural features result in the suppression of a space modulated cycloidal spin arrangement in the material. The latter manifests itself by the appearance of only single spectral component in the 57Fe Mössbauer spectrum of BiFeO3. The macroscopic magnetic behavior of the material is interpreted as a superposition of ferromagnetic and antiferromagnetic contributions with a large coercive field and remanent magnetization. Taking into account the average particle size of the as-prepared BiFeO3 particles (∼98 nm), exceeding the typical period length of cycloid (∼62 nm), both the suppression of the spiral spin structure in the material and its partly ferromagnetic behavior are attributed to the crystal lattice distortion caused by mechanical stress during the preparation procedure.

Bismuth ferrite (BFO) nanostructures and thin films have gained attraction as suitable candidates for energy storage and energy conversion due to their high energy storage efficiency, temperature stability and low dielectric loss. Electrical properties of such multiferroic materials are tailored by ferroelectric and ferromagnetic constituents and have opened up amazing avenues in electrochemical supercapacitor and photovoltaic applications. Dopants play a significant role in optimizing the magnetic and dielectric properties of such materials owing to suitable applications. This review highlights the scientific advancements reported in BFO nanostructures for energy applications by optimizing their magnetic and dielectric properties. This paper starts with a brief introduction of BFO and a discussion on the effects of various dopants by different synthesis techniques, and their effects on the magnetic and dielectric properties are also portrayed. Eventually, this review summarizes the various doping effects, which paves way for future research on this multiferroic material.

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.

The paper considers how a film of bismuth ferrite BiFeO3 (BFO) is formed on a polymeric flexible polyimide substrate at low temperature ALD (250 °C). Two samples of BFO/Polyimide with different thicknesses (42 nm, 77 nm) were studied. As the thickness increases, a crystalline BFO phase with magnetic and electrical properties inherent to a multiferroic is observed. An increase in the film thickness promotes clustering. The competition between the magnetic and electrical subsystems creates an anomalous behavior of the magnetization at a temperature of 200 K. This property is probably related to the multiferroic/polymer interface. This paper explores the prerequisites for the low-temperature growth of BFO films on organic materials as promising structural components for flexible and quantum electronics.

Eu1−xBaxTi1−yMyO3 (M = Co or Ni) was sintered at 1400 °C under a reduction atmosphere. X-ray photoelectron spectroscopy revealed the mixed valences of Eu2+/Eu3+ and Ti4+/Ti3+ in EuTiO3 and Eu0.7Ba0.3TiO3, as well as some oxygen vacancies required to keep the charge neutrality. The co-doping of Co2+/Ni2+ in Eu0.7Ba0.3TiO3 resulted in the disappearance of oxygen vacancies, as a result of a reduction in Ti3+ numbers and an increase in Eu3+ numbers. On the other hand, Ba2+ doping led to an increased lattice parameter due to its larger ionic size than Eu2+, whereas the Co2+/Ni2+ co-doping resulted in smaller lattice parameters because of the combined effects of ionic size and variation in the oxygen-vacancy numbers. Eu0.7Ba0.3TiO3 exhibited a clear ferroelectricity, which persisted in the Co2+/Ni2+ co-doped samples until the doping levels of y = 0.05 and 0.10, respectively. Eu0.7Ba0.3TiO3 remained to be antiferromagnetic with a reduced transition temperature of 3.1 K, but co-doping of Co2+/Ni2+ turned the samples from antiferromagnetic to ferromagnetic with transition temperatures of 2.98 K and 2.72 K, respectively. The cause for such a transition could not be explained by the larger lattice volume, oxygen vacancies and mixed valences of Eu2+/Eu3+, which were proposed in previous works. Instead, it was more likely to arise from a large asymmetric distortion of the Eu–O polyhedron introduced by the aliovalent doping, which promotes the admixture of Eu 5d and 4f states.

Abstract Lead-free magnetoelectric composites (1−x)K0.5Na0.5NbO3—(x)BaFe12O19 (x = 30, 40, and 50 wt%) are synthesized using solid state reaction method. X-ray diffraction (XRD) patterns confirm formation of diphase composites. Field emission scanning electron microscopy (FE-SEM) gives information about grain size, connectivity, and microstructure of constituent phases. Dielectric parameters of composite samples are studied as a function of temperature and the transition temperatures corresponding to both the constituent phases are observed in the composite samples. Dielectric constant has been found to decrease with addition of ferrite. Room temperature multiferroic behaviour has been confirmed using P-E and M-H hysteresis loops and magnetoelectric measurement. Polarization is found to decrease; however, magnetization increases with ferrite weight percentage. The highest α ME of 4.08 mV/(cm·Oe) is obtained for x = 30 wt% composite and it is realized that ferrite content significantly affects magnetoelectric behaviour.

BiFeO3 (BFO) is a multiferroic material with excellent ferroelectric properties but with poor magnetic behavior. Therefore, we focused principally on the enhancement of the magnetic order of BFO. These multiferroic properties make BFO an excellent candidate for magnetoelectric devices at room temperature. Pure and Co-BiFeO3 powders were successfully synthesized via the sol–gel method at 700 °C. The effect of Co substitution on the corresponding structural and magnetic properties of BFO was studied. X-ray diffraction and Fourier Transform Infrared Spectroscopy measurements confirmed the rhombohedral perovskite structure in all samples. A secondary phase of CoFe2O4 (CFO) was detected for 9, 10, and 15% of Co doping. The scanning electron microscopy images of the Co-BFO particles showed a reduction in the particle size compared to the pure BFO powders. Vibrating sample magnetometry measurements evidenced the ferromagnetic hysteresis loop for the Co-BFO powders with values of saturation magnetization of 4.1 emu/g and a coercivity of 1083 Oe for 15% of Co doping. In this work, we report impurity free samples with notable magnetic properties at the same time, which is a difficult challenge in bismuth ferrite synthesis. This is the first step for later applications in future technology.

Radial vortex-based spin torque nano-oscillators (RV-STNOs) have attracted extensive attention as potential nano microwave signal generators due to their advantages over other topological states, such as their higher oscillation, higher microwave power, and lower power consumption. However, the current driving the oscillation frequency of the STNOs must be limited in a small range of adjustment, which means less data transmission channels. In this paper, a new RV-STNO system is proposed with a multiferroic nanostructure, which consists of an ultrathin magnetic multilayer and a piezoelectric layer. Phase diagrams of oscillation frequency and amplitude with respect to piezostrain and current are obtained through micromagnetic simulation. The results show that the threshold current density of −4000-ppm compressive strain-assisted RV-STNOs is reduced from 2 × 109 A/m2 to 2 × 108 A/m2, showing one order of magnitude lower than that of conventional current-driven nano-oscillators. Meanwhile, the range of oscillation frequency adjustment is significantly enhanced, and there is an increased amplitude at the low oscillation point. Moreover, a promising digital binary frequency-shift key (BFSK) and binary amplitude-shift key (BASK) modulation technique is proposed under the combined action of current pulse and piezostrain pulse. They can transmit bit signals and show good modulation characteristics with a minimal transient state. These results provide a reference for developing the next generation of spintronic nano-oscillators with a wide frequency range and low power consumption, showing potential for future wireless communication applications.

Cobalt- Zinc ferrites are presently utilized as a significant component material for fabricating multiferroic composite. Conventional ceramic technique was utilized to synthesize the bulk cobalt-zinc ferrite with Mo substitution (CZFMO). In this present article, we accounted for the study of detail electric modulus and electrical conductivity of Co0.65Zn0.35Fe2-xMoxO4 (x=0.0, 0.1 and 0.2) spinel ferrites. The production of the inverse spinel nature of the material structure has been affirmed by the high resolution XRD pattern. The frequency reliance of real and imaginary part of electric modulus have been studied in detail. In the present framework the behavior of electric modulus could be communicated by the modified Kohlrausch-Williums-Watts (KWW) equation. The variation of the imaginary part of electric modulus (Mʺ) with frequency indicates the existence of non-Debye relaxation process in the current samples. The curves showing the variation of ac conductivity with frequency follow the Jonscher’s single power equation. This suggest that the conduction in the material is due to correlated barrier hopping (CBH) mechanism. Additionally, the conduction procedure can be best clarified based on Verwey-de Boer method. The activation energy in both ferromagnetic and paramagnetic area is assessed from the ln σac vs. 1/T curves. The temperature reliance of dc conductivity obeys the Arrhenius expression. Also the semiconducting nature of material has confirmed from the conductivity plot.

The electrical properties and behaviour in constant magnetic field of fourfold expanded GaSe matrix intercalated with SmCl 3 guest were investigated by means of impedance spectroscopy and cyclic voltammetry. It was determined that the synthesized GaSe< SmCl 3> clathrate of 4-fold expansion demonstrates the coexistence of mechanisms of generation, transformation and accumulation of electric energy on a quantum level. These mechanisms are driven from external sources of magnetic, thermal and electric field without Faradaic reactions. Therefore, investigated GaSe< SmCl 3> structure is of great attraction in multivoltaics as a prototype of new class of materials. Quantum mechanical model of electro motive force of spin nature is proposed. The main focus of work lies in the prospects of synthesized clathrates for the development of power nanosources and gyrator-free delay nanolines controlled by means of magnetic field.

Perovskites are among the most famous materials due to their exceptional properties: they present nearly all existing types of interesting properties, in particular as ferroics or multiferroics, they may be insulators, (super)conductors, or semiconductors, magnetoresistant, they are used in numerous devices, they present hundreds of variants and different crystalline phases and phase transitions, and recently appeared as probably the most promising materials for photovoltaics. With a crystal structure characterized by octahedra that share their corners, these materials belong to the wider category of « Framework Structure (FWS) materials » the structure of which is based on units (octahedra, tetrahedra, …) that share some of their corners (or edges) with their neighbours. This particular feature of FWS materials confers to them unique properties. This review volume is constituted of 26 chapters on different aspects, and is divided in two parts, « Fundamental aspects and general properties », and « Elaborated materials and applied properties ». Its main purpose is to attempt to identify the properties common to all members of the vast family of FWS materials, and understand their differences. Besides perovskites, derived compounds as 2D perovskites, Dion-Jacobson, Ruddlesden-Popper, Aurivillius, tungsten-bronzes, and others, are presented, and their preparation and/or properties as single crystals, ceramics, thin films, multilayers, nanomaterials, nanofibers, nanorods, etc, are discussed. We focus on new trends and important recent developments by leaving somewhat aside more classical aspects which can be easily found in older textbooks or review articles. Among most recent applications, this volume focuses on applications related with interactions with other molecules, on photovoltaics, and on memories, with a special attention to perovskite solar cells that have certainly attracted the most attention of researchers in recent years, opening extremely promising routes in photovoltaics. In conclusion, this book presents a collection of texts elucidating various aspects of the relation between structural organization (including dynamical aspects) and singular properties of framework crystals; it proposes a reasonable balance between experimental and theoretical results, and between fundamental aspects and applied properties. This volume can be approached on several levels (each chapter initially assumes that the reader is not a specialist in the subject, and is presented in a pedagogical way) : it is accessible to master or doctoral students, as well as to researchers who want to have informations on recent developments, who will find excellent detailed introductions up to hotsubjects. It may also be used by undergraduate students who should approach given subjects. The volume contains 800 pages written by about 70 authors from different countries, it has an index, and is completed by numerous figures to illustrate the text.

Pure BaZr0.2Ti0.8O3, pure Ni0.5Zn0.5Fe2O4, and 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4, 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4, and 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 multiferroic composites were prepared by a solid-state sintering method, and their structural, morphological, electrical (dielectric and ferroelectric), and magnetic properties were analyzed. A perovskite tetragonal phase (BaZr0.2Ti0.8O3) and a cubic spinel phase (Ni0.5Zn0.5Fe2O4) were simultaneously present in each composite. Peak shifting toward higher angles was observed for the 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4 and 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4 composites. BaZr0.2Ti0.8O3 part of all the composites demonstrated tensile strain value, while Ni0.5Zn0.5Fe2O4 part exhibited compressive strain values. A grain growth reduction phenomenon was observed with increasing Ni0.5Zn0.5Fe2O4 content in the composites. The largest average grain size was obtained for 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4 (933.23 ​nm), while the values for 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4 and 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 composites were 843.07 ​nm, 718.35 ​nm, respectively. All composites exhibited giant dielectric constants because of the electron hopping phenomenon between ​Fe2+and ​Fe3+. The 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 composite exhibited the highest dielectric constant of 88217.31 ​at 100 ​Hz. Similarly, it showed an enhanced dielectric loss of 2.77 (at 100 ​Hz). The 80BaZr0.2Ti0.8O3–20Ni0.5Zn0.5Fe2O4 composite exhibited the highest remnant polarization (13.58 ​μC ​cm−2), charge density (0.28 ​J ​cm−3), and discharge density (0.20 ​J ​cm−3) among the synthesized composites. However, 70BaZr0.2Ti0.8O3–30Ni0.5Zn0.5Fe2O4 exhibited the largest energy storage efficiency of 75%. Although pure BaZr0.2Ti0.8O3 did not show any response to an applied magnetic field, meaningful hysteresis loops were obtained for pure Ni0.5Zn0.5Fe2O4 and the (1-x)BaZr0.2Ti0.8O3-xNi0.5Zn0.5Fe2O4 composites. In addition, 60BaZr0.2Ti0.8O3–40Ni0.5Zn0.5Fe2O4 showed the highest saturation magnetization (17.52 emu/g) and remnant magnetization (0.92 emu/g) among the synthesized composites. Eventually, (1-x)BaZr0.2Ti0.8O3-xNi0.5Zn0.5Fe2O4 composites showed better performance compared to pure BaZr0.2Ti0.8O3 and Ni0.5Zn0.5Fe2O4 ceramics.

The key phenomena in multiferroic materials are their spontaneous polarization and magnetization. In order to meet the modern needs in the field of information technology and engineering, their coupling has been of great interest for generating marvel applications. Based on this idea, sol–gel auto-combustion method was utilized to synthesize BiFeO3 and MnFe2O4 which were moulded together in a composite by ball milling. For all the calcined samples of (1 − x)Bi0.9La0.1Fe0.9Mn0.1O3-(x)MnFe2O4 with different concentrations of MnFe2O4 i.e. at x = 0.00, 0.30, 0.50, 0.70 and 1.00, XRD was utilized for the analysis of crystal structure. It depicted the rhombohedral structure of BiFeO3 without any phase shifting throughout the samples, except at x = 1.00, for pure MnFe2O4, exhibiting cubic structure with no peak of BiFeO3 involved. Surface morphology was analysed using FESEM which confirmed that the granular size increased with the increase in MnFe2O4 concentration. For finding the weight percentage and elemental composition of the prepared composites, EDX analysis was carried out which revealed the presence of Bi, Mn, Fe, O, La in accordance with their stoichiometric formula. Vibrating sample magnetometry was put into use to inspect the magnetic properties of the synthesized composites and it was found that with the enhancement of MnFe2O4, magnetic characteristics were significantly improved. At last, precision multiferroic tester was used to examine the ferroelectric properties at 10 V. The PE loops, recoverable energy density, energy loss density and energy efficiency revealed a nice ferroelectric response in BiFeO3 dominating compositions. These interesting features uncovered the potential of these compositions for energy storage devices.

0.5AFeO3–0.5NaNbO3 (A=Bi, La) solid solution compositions were prepared using a solid phase reaction route from high-purity starting oxides. Mössbauer studies have shown that while for 0.5BiFeO3–0.5NaNbO3 the magnetic phase transition temperature TM value is about 150K, for 0.5LaFeO3–0.5NaNbO3, it is only ≈25K. This dramatic difference in TM values seems to be due to additional contribution of the magnetic superexchange between Fe3+ ions via the empty 6p-states of Bi3+ ions to the overall superexchange.

The potential of nanotechnology in the biomedical field has been crucial for contributing to the possibility of efficiently meeting present necessities with novel materials. Over the last few decades, nanostructures with a core/shell structure have attracted significant attention because of the possibility of changing their physical properties by varying their chemistry and geometry. These structures have become relevant in targeted therapy (drug delivery and treatments to complement chemotherapy and radiotherapy), imaging and in the stimulation of cellular functions. Thus in this paper the current development of core/shell nanostructures is reviewed, emphasizing the physical properties of those that have been proposed as potentially having biomedical applications, which are based in a magnetic behavior or in a mixture of magnetic and electric (multiferroic) phenomena.

Abstract In the present study, Zn-doped CaTiO3 nanocrystalline was synthesized to study the thermistor behavior with temperature. The X-ray powder diffraction analysis showed the formation of a single-phase orthorhombic structure at room temperature. The electrical resistance of the Zn-doped CaTiO3 increased with increasing doping concentration and decreased at higher measuring temperature, showing a negative temperature coefficient of resistance (NTCR) behavior. Different thermistor parameters were calculated using Steinhart–Hart equations, whilst time domain analysis confirmed faster response towards applied voltage.

Effects of Sr2+ substitution for La3+ on oxygen concentration and structure of La2-xSrxNiO4+δ have been observed by X-ray diffraction and Raman scattering. Oxygen concentration and unit cell volume of the material decrease monotonously in dependence of x. The vibration modes were calculated for La2NiO4 in K2NiF4 type structure with the group symmetry of I4/mmm. The Raman active modes for this symmetry were also theoretically identified. Raman back scattering spectra have been carried out for all the ceramic polycrystalline samples at room temperature. Two Raman lines at 224.6 cm-1 and 433 cm-1 , assigned to Eg and A1g vibration modes of oxygen O(II) in bonding La/Sr-O were observed for all the samples. The lower mode 224.6 cm-1 shifts down to 208 cm-1 , whereas the upper mode 433 cm-1 shifts up when concentration of the Sr substituting for La increases.