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Multiferroic composites are promising candidates for magnetic field sensors, next-generation low power memory and spintronic devices, as they exhibit much higher magnetoelectric (ME) coupling and coupled ordering parameters compared to the single-phase multiferroics. Hence, the 3-0 type particulate multiferroic composites having general formula (1 − Φ)[PbFe0.5Nb0.5O3]-Φ[Co0.6Zn0.4Fe1.7Mn0.3O4] (Φ = 0.0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, (1 − Φ) PFN-ΦCZFMO) were prepared using a hybrid synthesis technique. Preliminary structural and microstructural analysis were carried out using XRD and FESEM techniques, which suggest the formation of 3-0 type particulate composite without the presence of any impurity phases. The multiferroic behaviour of the composites is studied with polarization versus electric field (P-E) and magnetization versus magnetic field (M-H) characteristics at room temperature. The nature of ME coupling was investigated elaborately by employing the Landau free energy equation along with the magneto-capacitance measurement. This investigation suggests the existence of biquadratic nature of ME coupling (P2M2). The magneto-electric coupling measurement also suggests that strain mediated domain coupling between the ferroelectric and magnetic ordering is responsible for the magneto-electric behaviour. The obtained value of direct ME coefficient 26.78 mV/cm-Oe for Φ = 0.3, found to be higher than the well-known single-phase materials and polycrystalline composites.

Magnetoelectric (ME) heterostructures can exhibit higher magnetic and ferroelectric ordering temperatures along with large ME coupling compared to single-phase multiferroic materials. We synthesized Pb(Fe0.5Nb0.5)O3 (PFN)/Ni0.65Zn0.35Fe2O4 (NZFO)/Pb(Fe0.5Nb0.5)O3 (PFN)/Ni0.65Zn0.35Fe2O4 (NZFO)/Pb(Fe0.5Nb0.5)O3 (PFN) multilayer heterostructures having dimensions of 40/10/40/10/40 nm. High quality epitaxial growth of these heterostructures was confirmed via X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns. These nanostructures show well saturated polarization (∼52 μC cm−2) and magnetization (∼62 emu cm−3) at room temperature (RT). The magnetic and ferroelectric transitions occur well above RT. These heterostructures exhibit relaxor behavior and undergo 2nd order ferroelectric phase transition. Magnetodielectric measurements show significant coupling between the magnetic and electrical order parameters at RT. These characteristics of the heterostructures make them suitable as potential candidates for ultra-low power memory, spintronics, and different multifunctional (micro)nanoscale device applications.

This study reports the magnetocaloric effect (MCE) and piezoresponse of integrated ferroelectric-ferromagnetic heterostructures of PbZr 0.52Ti 0.48O 3 (PZT) (5 nm)/Bi-Sr-Ca-Cu 2-O X (BSCCO) (5 nm)/La 0.67Sr 0.33MnO 3 (LSMO) (40 nm)/MgO (0 0 1). Magnetic and pizoresponse behavior of the heterostructures are found to be governed by magneto-electric coupling and induced lattice strains. In addition, a maximum MCE is studied using Maxwell equations from both Field Cooled (FC) and Zero Field Cooled (ZFC) magnetization data. Maximum MCE entropy change (|ΔS|) of 42.6 mJkg −1K −1 (at 258 K) and 41.7 mJkg −1K −1 (at 269 K) are found corresponding to FC and ZFC data, respectively. The variation in maximum entropy change and corresponding temperatures for FC and ZFC data revealed that the application of a magnetic field can significantly contribute towards tuning of the MCE. Interestingly, these multilayered structures are found to sustain MCE over a broad temperature range, which makes them attractive for improved solid-state energy conversion devices.

One of the ways to mitigate the world energy crisis is to harvest clean and green energy from waste-heat, which is abundant, ubiquitous, and free. Energy harvesting of this waste-heat is one of the most encouraging methods to capture freely accessible electrical energy. Ferroelectric materials can be used to harvest energy for low power electronic devices, as they exhibit switchable polarization, excellent piezoelectric and pyroelectric properties. The most important characteristic of ferroelectric materials, in the context of energy harvesting, is their ability to generate electric power from a time-dependent temperature change. In this work, we grew highly c-axis oriented heterostructures of BaZr0.2Ti0.8O3 (barium zirconium titanate, BZT)/Ba0.7Ca0.3TiO3 (barium calcium titanate, BCT) on SrRuO3 (strontium ruthenate, SRO) and deposited on SrTiO3 (strontium titanate, STO) single crystalline substrate using pulsed laser deposition (PLD) technique. We investigated the structural, electrical, dielectric, and pyroelectric properties of the above-mentioned fabricated heterostructures. The wide range of θ–2θ X-ray diffraction (XRD) patterns only shows (00l) reflection peaks of heterostructures and the substrate which confirmed that the films are highly c-axis oriented. We are also capable to convert the low-grade waste-heat into electrical energy by measuring various temperature-dependent ferroelectric hysteresis loops of our nanostructure films via pyroelectric Ericsson cycles and the structures show an energy conversion density ~ 10,970 kJ/m3 per cycle. These devices exhibit a large pyroelectric current density of ~ 25 mA/m2 with 11.8 °C of temperature fluctuation and the corresponding pyroelectric coefficient of 3425 μC/m2K. Our research findings suggest that these lead-free relaxor-ferroelectric heterostructures might be the potential candidates to harvest electrical energy from waste low-grade thermal energy.

Multiferroic (MF)-magnetoelectric (ME) composites, which integrate magnetic and ferroelectric materials, exhibit a higher operational temperature (above room temperature) and superior (several orders of magnitude) ME coupling when compared to single-phase multiferroic materials. Room temperature control and the switching of magnetic properties via an electric field and electrical properties by a magnetic field has motivated research towards the goal of realizing ultralow power and multifunctional nano (micro) electronic devices. Here, some of the leading applications for magnetoelectric composites are reviewed, and the mechanisms and nature of ME coupling in artificial composite systems are discussed. Ways to enhance the ME coupling and other physical properties are also demonstrated. Finally, emphasis is given to the important open questions and future directions in this field, where new breakthroughs could have a significant impact in transforming scientific discoveries to practical device applications, which can be well-controlled both magnetically and electrically.

Varying the substrate temperature changes structural and magnetic properties of spinel ferrite Ni0.65Zn0.35Fe2O4 (NZFO) thin films. X-ray diffraction of films grown at different temperature display only (004) reflections, without any secondary peaks, showing growth orientation along the c-axis. We find an increase in crystalline quality of these thin films with the rise of substrate temperature. The surface topography of thin films grown at different growth temperatures reveal that these films are smooth with low roughness; however, the thin films grown at 800 °C exhibit lowest average and root mean square (rms) roughness among all thin films. We find iron and nickel to be more oxidized (greater Fe3+ and Ni3+ content) in films grown and annealed at 700 °C and 800 °C, compared to those films grown at lower temperatures. The magnetic moment is observed to increase with an increase of substrate temperature and all thin films possess high saturation magnetization and low coercive field at room temperature. Films grown at 800 °C exhibit a ferrimagnetic–paramagnetic phase transition well above room temperature. The observed large magnetizations with soft magnetic behavior in NZFO thin films above room temperature suggest potential applications in memory, spintronics, and multifunctional devices.

Ba0.70Sr0.30TiO3-(BST) ceramics were fabricated by conventional mixed oxide route. The structural phase transition, ferroelectric, dielectric and energy storage properties of BST ceramics capacitor...

We grew lead-free BaZr0.2Ti0.8O3 (BZT)/Ba0.7Ca0.3TiO3 (BCT) epitaxial heterostructures and studied their structural, dielectric, ferroelectric and energy density characteristics. The BZT/BCT epitaxial heterostructures were grown on SrRuO3 (SRO) buffered SrTiO3 (STO) single crystal substrate by optimized pulsed laser deposition (PLD) technique. These high-quality nanostructures exhibit high dielectric permittivity (∼1300), slim electric field-dependent polarization (P-E) curve with high saturation polarization (∼100 µC/cm2) and low remnant polarization (∼20 µC/cm2) through interface engineering to develop new lead-free ferroelectric system for energy storage devices. We observe an ultrahigh discharge and charge energy densities of 42.10 and 97.13 J/cm3, respectively, with high efficiency, which might be highly promising for both high power and energy storage electrical devices.

Multiferroic composites with enhanced magneto-electric coefficient are suitable candidates for various multifunctional devices. Here, we chose a particulate composite, which is the combination of multiferroic (PbFe0.5Nb0.5O3, PFN) as matrix and magnetostrictive (Co0.6Zn0.4Fe1.7Mn0.3O4, CZFMO) material as the dispersive phase. The X-ray diffraction analysis confirmed the formation of the composite having both perovskite PFN and magnetostrictive CZFMO phases. The scanning electron micrograph (SEM) showed dispersion of the CZFMO phase in the matrix of the PFN phase. The temperature-dependent magnetization curves suggested the transition arising due to PFN and CZFMO phase. The temperature-dependent dielectric study revealed a second-order ferroelectric to the paraelectric phase transition of the PFN phase in the composite with a small change in the transition temperature as compared to pure PFN. The magnetocapacitance (MC%) and magnetoimpedance (MI%) values (obtained from the magneto-dielectric study at room temperature (RT)) at 10 kHz were found to be 0.18% and 0.17% respectively. The intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm−1Oe−1, which is comparable to other typical multiferroic composites in bulk form. The composite PFN-CZFMO exhibited a converse magneto-electric effect with a change in remanent magnetization value of −58.34% after electrical poling of the material. The obtained outcomes from the present study may be utilized in the understanding and development of new technologies of this composite for spintronics applications.

Bimetallic alloys with large discrepancies in atomic radii and crystal structure typically yield systems that are highly immiscible, even at high temperatures. The AgxFe1−x binary system has limited solid and liquid solubility and thus phase separated Ag + Fe alloys should result. Furthermore, Ag has interesting plasmonic properties and Fe is a strong ferromagnet, thus magneto-plasmonic nanoparticles/films should result due to their phase separation. We have leveraged a combinatorial sputter deposition to synthesize thin films with a large AgxFe1−x (0.19

This article presents the effect of lead-borosilicate glass (65PbO 20B 2 O 3 15SiO 2 , mol%) (PBS) addition on the structure, microstructure, dielectric, ferroelectric and energy storage properties of Ba 0.9995 La 0.0005 TiO 3 (BLT) ceramics system has been systematically investigated. XRD analysis revealed the tetragonal (T) phase at room temperature. Addition of PBS glass results in decrease in ferroelectricity and improved breakdown properties. High maximum polarization (P s ∼21.53 μC/cm 2 ) and remnant polarization values (2P r ∼8.75 μC/cm 2 ) were obtained from ferroelectric (P-E) hysteresis loops for the BLT ceramics. Two dielectric anomalies at 420 K and 600 K were observed due to the phase transformation. The glass-ceramics heat treated at 900 °C for 3 h was found to possess optimal properties with breakdown strength of >300 kV/cm and energy storage density of 0.564 J/cm 3 , which is a promising glass-ceramic ferroelectric capacitor material for high energy storage density dielectrics.

We report a detailed investigation on magnetic and electrical properties of the multiferroic GaFeO3 (GFO) thin films grown on SrRuO3 (SRO) buffered SrTiO3 (1 1 1) substrates. The magnetic transition temperature (Tc) of GFO thin films is observed ∼240 K, which is higher by 20 K than in GFO ceramic. The clear and reversible out-of-plane phase-contrast seen in the Piezoresponse Force Microscopy (PFM) phase and amplitude images measured within positive and negative poling confirms the polarization reorientation and hence piezoelectric nature of the compound. The temperature and frequency dependence of permittivity studies demonstrates the relaxor behavior of these thin films. The observed near room temperature (RT) magnetic phase transition with RT piezoelectric nature of these thin films elucidates the possible potential candidates for a multiferroic world with spintronics device applications.

Magnetoelectric (ME) composite thin films are promising candidates for novel applications in future nanoelectronics, spintronics, memory, and other multifunctional devices as they exhibit much higher ME coupling and transition temperatures (Tc) than well-known single phase multiferroics discovered to date. Among the three types of multiferroic composite nanostructures, (2–2) layered and (1–3) vertically aligned composite nanostructures exhibit comparatively smaller ME coupling due to different shortcomings that restrict their use in many applications. Here, we study the morphological, piezoresponse force microscopic (PFM), ferroelectric, magnetic, and magnetodielectric properties of 0–3 [magnetic nanoparticles (0) homogeneously distributed in ferroelectric matrices (3)] multiferroic composite thin films. The Pb(Fe0.5Nb0.5)O3 (PFN)–Ni0.65Zn0.35Fe2O4 (NZFO) particulate composite films were synthesized by pulsed laser deposition. These particulate composite thin films are completely c-axis oriented with very low surface roughness. We observed magnetic and ferroelectric Tc above room temperature (RT) for all composite thin films. The PFN–NZFO 0–3 composites exhibit large polarization, high saturated magnetization with low coercive field, and low dielectric loss along with magnetodielectric coupling at RT. These nanocomposites might be utilized in next generation nano/microelectronics and spintronic devices.

Modifying Fe and Mn contents in GaFeO3 (GFO) enhances the magnetic properties, increases the magnetic transition temperature (TC) and reduces the leakage current. Here, we report structural, magnetic, and leakage current characteristics of manganese-doped gallium ferrite with different Fe-content, i.e. Ga2−xFexO3 (1 ≤ x ≤ 1.4) system. Structural characterization reveals that all the samples retain the orthorhombic phase with space group Pc21n for above amounts of doping. Magnetization of the samples with respect to temperature shows the lower magnetic transition temperature (TC) for pure GFO, i.e. 220 K, which increases to 345 K above room temperature (RT) for 2% Mn-doped Ga0.6Fe1.4O3 (GFMO3). Higher remanent magnetization (~16 emu g−1) with a lower coercive field (~4 kOe) is obtained for Mn-doped Ga0.6Fe1.4O3. We found the decrease of leakage current with doping of Mn. The observation of multiferroicity in these single-phase materials (i.e. GFO3 and GFMO3) at RT make them potential candidates for memory, multifunctional, and spintronics device applications.

Multiferroic materials have attracted considerable attention as possible candidates for a wide variety of future microelectronic and memory devices, although robust magnetoelectric (ME) coupling between electric and magnetic orders at room temperature still remains difficult to achieve. In order to obtain robust ME coupling at room temperature, we studied the Pb(Fe0.5Nb0.5)O3/Ni0.65Zn0.35Fe2O4/Pb(Fe0.5Nb0.5)O3 (PFN/NZFO/PFN) trilayer structure as a representative FE/FM/FE system. We report the ferroelectric, magnetic and ME properties of PFN/NZFO/PFN trilayer nanoscale heterostructure having dimensions 70/20/70 nm, at room temperature. The presence of only (00l) reflection of PFN and NZFO in the X-ray diffraction (XRD) patterns and electron diffraction patterns in Transmission Electron Microscopy (TEM) confirm the epitaxial growth of multilayer heterostructure. The distribution of the ferroelectric loop area in a wide area has been studied, suggesting that spatial variability of ferroelectric switching behavior is low, and film growth is of high quality. The ferroelectric and magnetic phase transitions of these heterostructures have been found at ~575 K and ~650 K, respectively which are well above room temperature. These nanostructures exhibit low loss tangent, large saturation polarization (Ps ~ 38 µC/cm2) and magnetization (Ms ~ 48 emu/cm3) with strong ME coupling at room temperature revealing them as potential candidates for nanoscale multifunctional and spintronics device applications.

We show the ability to map the phase diagram of a relaxor-ferroelectric system as a function of temperature and composition through local hysteresis curve acquisition, with the voltage spectroscopy data being used as a proxy for the (unknown) microscopic state or thermodynamic parameters of materials. Given the discrete nature of the measurement points, we use Gaussian processes to reconstruct hysteresis loops in temperature and voltage space, and compare the results with the raw data and bulk dielectric spectroscopy measurements. The results indicate that the surface transition temperature is similar for all but one composition with respect to the bulk. Through clustering algorithms, we recreate the main features of the bulk diagram, and provide statistical confidence estimates for the reconstructed phase transition temperatures. We validate the method by using Gaussian processes to predict hysteresis loops for a given temperature for a composition unseen by the algorithm, and compare with measurements. These techniques can be used to map phase diagrams from functional materials in an automated fashion, and provide a method for uncertainty quantification and model selection. The functional response of piezoelectrics for arbitrary compositions and conditions cannot be fully obtained using local probes. Although the ferroelectric to paraelectric phase transition temperature can be measured, this is only for a limited number of data points. Now, a team led by Rama Vasudevan at Oak Ridge National Laboratory and colleagues in Puerto Rico, the United States, and India demonstrate that machine learning can be used to obtain the full ferroelectric phase diagram, with functional response. From measurements on four samples of a material, they use a machine-learning technique called Gaussian processes to reconstruct piezoelectric properties for continuously varying voltages and temperatures, which with more commonly used approaches accurately predicts ferroelectric phase diagrams. This could be used to generate piezoelectric phase diagrams, highlighting material compositions with optimal properties that can then be targeted by synthesis.

We report studies of the ferroelectric and magnetic phase transitions of (1 – x)Pb(Fe0.5Nb0.5)O3 – xCo0.65Zn0.35Fe2O4 (x = 0.2) composite with emphasis upon the nature of magnetoelectric coupling at room temperature. The presence of all cationic elements with their required stoichiometry have been confirmed by SEM and XPS studies. The composite shows well-saturated ferroelectric and ferromagnetic (multiferroic) behavior at room temperature. A ferroelectric-paraelectric phase transition has been confirmed from the temperature dependent dielectric spectra along with DSC and Raman spectroscopic studies. Antiferromagnetic, ferromagnetic, and relaxor paramagnetic states have been observed in this composite. This composite shows strong bulk biquadratic magnetoelectric coupling at room temperature, which can be useful for potential multifunctional device applications.

In this chapter a detailed discussion on multilayers architectures is provided to understand their transport properties, tunneling current, interface behavior at atomic scale, and compatibility with silicon and state of the art technology. The chapter deals with the fabrication process and functional properties of multilayer and superlattice structure on various substrates for possible applications as multistates nonvolatile random access memory and logic devices. It starts with an introduction and then explains the concept of spintronics and multistates logics and finally correlates the microstructure with device properties. Various device architectures such as metal–insulator–metal, metal-ferroelectric–metal, metal-ferromagnetic/multiferroic-metal, metal (ferromagnetic)–multiferroic-metal (anti/ferromagnetic), silicon-ferroelectric/multiferroic-metal, ferromagnetic–multiferroic-metal, etc. heterostructures are discussed and explained their suitability as multistates logics and memory devices, possible drawbacks and potential to win the international market. This chapter covers the state of art development of ferroelectric/multiferroic tunnel junctions and possible future spin-devices. A tunneling electroresistance for the realization of intrinsic ferroelectric polarization has been discussed.

Palladium normally does not easily substitute for Ti or Zr in perovskite oxides. Moreover, Pd is not normally magnetic (but becomes ferromagnetic under applied uniaxial stress or electric fields). Despite these two great obstacles, we have succeeded in fabricating lead zirconate titanate with 30% Pd substitution. For 20:80 Zr:Ti, the ceramics are generally single-phase perovskites (g99%) but sometimes exhibit 1% PdO, which is magnetic at room temperature. The resulting material is multiferroic (ferroelectric-ferromagnetic) at room temperature. The processing is slightly unusual (g8 h in high-energy ball-milling in Zr balls), and the density functional theory provided shows that it occurs because of $\mathrm{P}{\mathrm{d}}^{+4}$ in the oversized $\mathrm{P}{\mathrm{b}}^{+2}$ site; if all $\mathrm{P}{\mathrm{d}}^{+4}$ were to go into the $\mathrm{T}{\mathrm{i}}^{+4}$ perovskite B site, only a small moment of 0.1 Bohr magnetons would result.

Magnetoelectric (ME) materials with ferroelectric and magnetic transition temperatures near room temperature are of current interest in research due to their technological importance and potential applications. Herein, we report the coupled magnetic ordering and phonons in gallium ferrite (GaFeO3), a near room temperature ME perovskite, using magnetization and inelastic light scattering measurements as a function of temperature. Temperature-dependent magnetization behavior studied in a wide temperature range of 5–395 K at both field-cooled (FC) and zero-field-cooled (ZFC) conditions using different static magnetic fields confirms the magnetic transition temperature Tc at 220 K. On temperature dependent Raman spectroscopy, no significant changes in Raman spectra were observed at an elevated temperature that can be attributed to the absence of structural phase transition. Instead of expected anharmonic behavior, several librational (rigid rotation) and stretching modes of rigid BO6 units were found to be hardening below Tc, suggesting the significant magnetoelastic coupling contributions to phonon frequencies. The asymmetric stretching mode at 753 cm−1 is found to have larger spin-phonon coupling contribution (λ∼2.93), while the lattice mode at 153 cm−1 and external librational mode at 240 cm−1 had the lowest effect (λ∼0.88).

Multiferroic composite structures, i.e., composites of magnetostrictive and piezoelectric materials, can be envisioned to achieve the goal of strong room-temperature ME coupling for real practical device applications. Magnetic materials with high magnetostriction, high Neel temperature (TN), high resistivity and large magnetization are required to observe high ME coupling in composite structures. In continuation of our investigations on suitable magnetic candidates for multiferroic composite structures, we have studied the crystal structure, dielectric, transport, and magnetic properties of Co0.65Zn0.35Fe2O4 (CZFO). Rietveld refinement of X-ray diffraction patterns confirms the phase purity with a cubic crystal structure with the (Fdm) space group; however, we have found a surprisingly large magneto-dielectric anomaly at the Neel temperature, unexpected for a cubic structure. The presence of mixed valences of Fe2+/Fe3+ cations is probed by X-ray photoelectron spectroscopy (XPS), which supports the catonic ordering-mediated large dielectric response. Large dielectric permittivity dispersion with a broad anomaly is observed in the vicinity of the magnetic phase transition temperature (TN) of CZFO suggesting a strong correlation between dielectric and magnetic properties. The evidence of strong spin-polaron coupling has been established from temperature dependent dielectric, ac conductivity and magnetization studies. The ferrimagnetic–paramagnetic phase transition of CZFO has been found at ∼640 K, which is well above room temperature. CZFO exhibits low loss tangent, a high dielectric constant, large magnetization with soft magnetic behavior and magnetodielectric coupling above room temperature, elucidating the possible potential candidates for multiferroic composite structures as well as for multifunctional and spintronics device applications.

Piezoelectric and other physical properties are significantly enhanced at (or near) a morphotropic phase boundary (MPB) in ferroelectrics. MPB materials have attracted significant attention owing to both fundamental physics as well as the possibility of well-regulated energy and information storage devices which are dominated by lead (Pb)-based materials. Here, we report the crystal structure, Raman spectra, dielectric constant and polarization near the MPB of lead free (1 - x) Na0.5Bi0.5TiO3 - x BaTiO3 (0.00 ⩽ x ⩽ 0.10) solid-solution, prepared by sol-gel auto combustion technique and sintered by microwave sintering technique. With the addition of BaTiO3 into Na0.5Bi0.5TiO3, it induces a structural phase transition from R3c (a single phase) to R3c + P4mm (a dual phase) close to x = 0.06 and 0.07 and transform to a high symmetry tetragonal phase P4mm at higher compositions (x = 0.08 to 0.10) as evident from our x-ray Rietveld refinement and Raman spectroscopic results. We perform first-principles calculations based on density functional theory that confirm a structural transition from a rhombohedral to a tetragonal phase under increasing x. In the prepared solid solution, an anomalous enhancement of remnant polarization ([Formula: see text]) was observed for x = 0.06 and 0.07, which has been explained based on the existence of the MPB. On the other hand, the value of coercive field [Formula: see text] was found to be decreased linearly from x = 0.00 to 0.06; it is constant for higher compositions. Further details of the ferroelectric properties on the electric field poled samples have been studied and compared with the as-grown (unpoled) samples.

With the development of electronic devices towards miniaturization, light weight and integration, dielectric thin film-capacitors for recoverable energy storage applications have attracted ever-growing interests owing to their fast charging and discharging rate. In continuation to our investigations for achieving high energy density, we have grown lead free BaZr0.2Ti0.8O3 (BZT)/Ba0.7Ca0.3TiO3 (BCT) heterostructures and studied the structural, dielectric, ferroelectric and energy density characteristics. The BZT/BCT bilayer epitaxial heterostructures were grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 (LAO) single crystal substrate by optimized pulsed laser deposition technique. The ferroelectric phase transition has been probed above room temperature with relaxor behavior. These nanostructures show high discharge and charge energy densities of 9.74 and 26.55 J/cm3, respectively. These heterostructures show high dielectric permittivity, large polarization and high energy density characteristics well above room temperature which may be useful for both high power and energy density device applications.

Highly sensitive large-scale tin oxide (SnO2) nanostructures were grown on a glass substrate by thermal evaporation of a mixture of anhydrous tin (II) chloride (SnCl2) and zinc chloride (ZnCl2) powders at 550°C in air. We demonstrate a single cell vapor deposition system to precisely control nanostructural morphology of SnO2 by changing the weight ratio of SnCl2 and ZnCl2 and growth temperature. The morphology and structural property of as-grown nanostructures were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SEM images revealed that the SnO2 nanostructures with different densities, sizes, and shapes can be achieved by adjusting the weight ratio of SnCl2 and ZnCl2. A thin film gas sensor based on SnO2 nanostructures with diameter ∼20 nm and length ∼100 nm showed ∼85% sensitivity and 53 seconds of response time, whereas the nanorods with diameter ∼100 nm and length ∼ 1μm showed ∼50% sensitivity with 198 seconds response time. The nanostructured material with small size and shape showed better sensitivity on sensing at room temperature compared to previously reported SnO2 based sensors.

Nanoscale switchable ferroelectric (Ba0.50Sr0.50)(Ti0.80Sn0.20)O3-BSTS polycrystalline thin films with a perovskite structure were prepared on Pt/TiOx/SiO2/Si substrate by chemical solution deposition. X-ray diffraction (XRD) spectra indicate that a cubic perovskite crystalline structure and Raman spectra revealed that a tetragonal perovskite crystalline structure is present in the thin films. Sr2+and Sn4+cosubstituted film exhibited the lowest leakage current density. Piezoresponse Force Microscopy (PFM) technique has been employed to acquire out-of-plane (OPP) piezoresponse images and local piezoelectric hysteresis loop in polycrystalline BSTS films. PFM phase and amplitude images reveal nanoscale ferroelectric switching behavior at room temperature. Square patterns with dark and bright contrasts were written by local poling and reversible nature of the piezoresponse behavior was established. Local piezoelectric butterfly amplitude and phase hysteresis loops display ferroelectric nature at nanoscale level. The significance of this paper is to present ferroelectric/piezoelectric nature in present BSTS films at nanoscale level and corroborating ferroelectric behavior by utilizing Raman spectroscopy. Thus, further optimizing physical and electrical properties, BSTS films might be useful for practical applications which include nonvolatile ferroelectric memories, data-storage media, piezoelectric actuators, and electric energy storage capacitors.

Vanadium oxide (VO2) thin films have drawn significant research and development interest in recent years because of their intriguing physical origin and wide range of functionalities useful for many potential applications, including infrared imaging, smart windows, and energy and information technologies. However, the growth of highly epitaxial films of VO2, with a sharp and distinct controllable transition, has remained a challenge. Here, we report the structural and electronic properties of high quality and reproducible epitaxial thin films of VO2, grown on c-axis oriented sapphire substrates using pulsed laser deposition at different deposition pressures and temperatures, followed by various annealing schedules. Our results demonstrate that the annealing of epitaxial VO2 films significantly enhances the Semiconductor to Metal Transition (SMT) to that of bulk VO2 transition. The effect of oxygen partial pressure during the growth of VO2 films creates a significant modulation of the SMT from around room ...

The search for a room temperature single phase multiferroic material displaying strong magnetoelectric coupling and low leakage current for practical device applications has been underway and a long-standing challenge. In continuation to our investigations for achieving robust ME coupling and enhanced electrical insulation at room temperature, we report magnetic, electrical insulation, and magneto-dielectric properties of Nd and Mn co-doped BiFeO3 (Bi0.95Nd0.05)(Fe0.97Mn0.03)O3 (BNFM) polycrystalline electro-ceramics. Magnetic studies have been carried out in two different temperature regions, i.e., 15–300 K and 300–800 K. The doping of Nd and Mn in the BiFeO3 (BFO) lattice slightly reduces the Neel temperature (TN) with broad weak ferromagnetic (FM) to paramagnetic (PM) phase transition by increasing ferromagnetic domain fractions. A small amount of magnetic frustration is also found in the low temperature regions, below 300 K at fields of 100 and 200 Oe, and below 200 K at higher field cooled and zero f...

With the rapid development of new device miniaturization technology, there is invigorated interest in magnetic nanostructures for potential application in novel multifunctional devices. In continuation to our search for a suitable magnetic material having Curie temperature (Tc) well above room temperature for multifunctional applications, we have studied the dielectric, optical, magnetic, and resistance switching characteristics of Ni0.65Zn0.35Fe2O4 (NZFO) thin films. The observation of only (004) reflection in the X-ray diffraction patterns confirms the c-axis orientation and high quality growth of NZFO thin films. The presence of mixed valences of Fe2+/Fe3+ cations is probed by X-ray photon spectroscopy, which supports the cationic ordering-mediated large dielectric response. Our investigations reveal NZFO to be an indirect band gap material (∼1.8 eV) with a direct gap at ∼2.55 eV. These nanostructures exhibit high saturation magnetization and a low coercive field with a ferrimagnetic–paramagnetic phase transition of ∼713 K. Magnetic force microscopy studies revealed the stripe-like domain structure of the investigated thin films. In addition, these thin films exhibit reliable and repeatable unipolar resistive switching characteristics. The observed high dielectric permittivity with low loss tangent, large magnetization with soft magnetic behavior, striped magnetic domain structure and reliable resistance switching in NZFO thin films above room temperature suggest potential application in memory, spintronics, and multifunctional devices.

We report photovoltaic (PV) effect in multiferroic Bi0.9Sm0.1Fe0.95Co0.05O3 (BSFCO) thin films. Transition metal modified polycrystalline BiFeO3 (BFO) thin films have been deposited on Pt/TiO2/SiO2/Si substrate successfully through pulsed laser deposition (PLD). PV response is observed under illumination both in sandwich and lateral electrode configurations. The open-circuit voltage (V-oc) and the short-circuit current density (J(sc)) of the films in sandwich electrode configuration under illumination are measured to be 0.9 V and -0.051 mu A cm(-2). Additionally, we report piezoresponse for BSFCO films, which confirms ferroelectric piezoelectric behaviour.