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Interface-engineered superlattices composed of perovskite PrCoO3 and brownmillerite CaCoO2.5 ([(PCO)n/(CCO)n]m) were designed and fabricated on (001) SrTiO3 substrates with integrated antiphase domain boundaries (APBs) for investigating ferromagnetic insulating phenomenon. The APBs were formed at the surface-step-terrace edges, and the densities of APBs can be regulated by the periods of the superlattices. In these superlattices, ferromagnetic insulating properties were found to be significantly modulated by the APBs. The room-temperature resistivity of the n = 1 superlattice increases by more than three orders of magnitude than that of the n = 5 superlattice and more than five orders of magnitude than that of the Pr0.5Ca0.5CoO3-δ alloy films. The insulation behavior is primarily derived from the charge carriers scattering at the APBs, which block the charge carriers transferring along the in-plane direction. These results could propel the advancement of multifunctional material genetics and provide a strategic approach for the development of artificial materials with tunable properties. [ABSTRACT FROM AUTHOR]

The electrical boundary condition plays an important role in the manipulation of domain structures in low-dimensional ferroelectric materials, especially ferroelectric nanowires. Here, using phase-field simulations, we systematically investigate the influence of electrical boundary conditions on the domain structure in porous PbTiO3 ferroelectric nanowires. Our results demonstrate the formation of four types of domain structures via varying electrical boundary conditions, which possess distinguished local polarization and energy configurations. We further show that the domain structures are also dependent on the nanowire radius, including the breakdown of a metastable concentric toroidal domain structure upon reducing the radius to 14 nm. The present work provides guidance for further experimental studies on the control of polar domain structures through manipulating the electrical boundary condition and the ferroelectric size, which paves the way for developing multi-functions of low-dimensional ferroelectric systems. [ABSTRACT FROM AUTHOR]

Dielectric materials featured with polarization at an applied electric field have been demonstrated with a wide range of applications such as energy storage and conversion, thus triggering tremendous efforts in scientific and industrial research. To date, numerous strategies have been explored to improve the performance of dielectric materials; especially, the recently reported high-entropy design enabling flexible composition configuration and tunable functional properties has attracted increasing attention. In this contribution, we review the very recent investigations and applications of high-entropy design for dielectric materials, including dielectric energy storage, electrocalorics, piezoelectrics, and ferroelectrics, and address the challenges and remaining concerns. Finally, we suggest future research directions for the preparation and in-depth structure characterization of high-entropy dielectric materials. This review will provide a holistic view of the most state-of-the-art high-entropy dielectric materials and envision prospects of high-entropy design for dielectrics. [ABSTRACT FROM AUTHOR]

Polymer blends are regarded as a straightforward and effective method to enhance the energy storage performance of dielectric film capacitors. However, how the components and structures within the blend systems affect the energy density and efficiency remains insufficiently explored in-depth. In this discourse, employing a polymer blend of ferroelectric and linear dielectric phases as a paradigm, we perform phase-field simulations to elucidate the effects of ferroelectric phase volume fractions, geometrical dimensions, and the dielectric constant of the linear phase on the energy storage capabilities. Concurrently, we have devised six divergent blending microstructures to probe the ramifications of structural variances on the overarching performance metrics. We also analyze the domain configurations and switching dynamics under varying electric fields to understand the performance variations and delineate the determinants conducive to superior energy density and efficiency. This paper theoretically establishes the component–content–structure–performance relationships of different polymer blend systems, which is expected to better guide the innovative design of new polymer blend dielectrics. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride)-based ferroelectric polymers, known for their exceptional flexibility, cost-effectiveness, and ease of processing, have garnered significant attention in the field of nonvolatile data storage. However, a persistent challenge lies in their elevated driving voltage and subpar thermal stability, leading to excessive power consumption and restricted operational conditions. Herein, we propose a flexible ferroelectric random access memory (FeRAM) based on a ceramic/polymer bilayer consisting of a solution-processed ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] nanofilm on top of a TiO2 nanolayer. The polarized Fourier transform infrared spectroscopy spectra and piezoresponse force microscopy phase signals demonstrate that the surface effect of the underlying TiO2 induces a consistent dipole orientation along the out-of-plane direction in the P(VDF-TrFE) nanofilm. These aligned dipoles in the P(VDF-TrFE) can be efficiently switched by a low driving voltage of 5 V while maintaining a high thermal stability exceeding 100 °C. Furthermore, the FeRAM based on the TiO2/P(VDF-TrFE) bilayer exhibits a remarkable storage density of approximately 60 GB in.–2, coupled with exceptional flexibility, high transparency, and superior read/write durability. These outstanding performances indicate that the TiO2/P(VDF-TrFE) bilayer holds significant potential for applications in high-density information storage within flexible electronics. [ABSTRACT FROM AUTHOR]

To meet the miniaturization demands of next-generation electronics and electrical systems, energy storage capacitors with both high energy density and efficiency have become a research hotspot. Ferroelectric-based dielectrics are primary candidates due to the existence of spontaneous polarization and versatile domain structures. Since domains are fundamental structure units that respond to the external electric field, domain engineering is a general route to realizing high energy storage performance. In this perspective, we introduce a type of dielectrics, proposed recently and termed superparaelectrics, which has ultrasmall polar clusters (several unit cells) and exhibits nearly zero hysteresis and relatively high polarization due to the highly dynamical polar structure. Fundamental concepts of superparaelectricity are overviewed, and representative examples with state-of-the-art energy storage performance are reviewed to demonstrate the advantages of superparaelectrics. Finally, perspectives are provided about the future development of superparaelectric and electrostatic energy storage fields. [ABSTRACT FROM AUTHOR]

Future applications in power generation for wearable and portable electronics or active cooling for chips will benefit from near-room-temperature thermoelectric performance enhancement. Ga-doped ZnO (GZO) thin films are potential thermoelectric materials as they have the advantages of high cost-effectiveness, low toxicity, excellent stability, and high optical transparency. Inserting a ZnO buffer layer between the sapphire substrate and GZO thin films could contribute to optimizing carrier mobility and further improving electrical transport properties. However, thermoelectric performance at near-room-temperature ranges still needs to be promoted for practical applications. In this present study, ZnO single-crystal slices were directly selected as substrates for homogenously growing GZO thin films to further modify the substrate–film interface. The high Hall mobility of 47 cm2 V−1 s−1 and weighted mobility of 75 cm2 V−1 s−1 could be realized, resulting in better electrical transport performance. Consequently, the homogenously grown GZO thin films possessed competitively prominent power factor values of 333 μW m−1 K−2 at 300 K and 391 μW m−1 K−2 at 373 K. This work offers an effective avenue for optimizing the thermoelectric properties of oxide-based thin films via homogenous growth. [ABSTRACT FROM AUTHOR]

Understanding the microscopic origin of exotic domain configurations and emergent properties in charged domain walls is essential for both fundamental physics and applications in next-generation nanoelectronics. In self-assembled BiFeO3 nanoislands, 71° ferroelastic charged domain walls were spontaneously formed, which were traditionally regarded as unstable architectures. Here, by combining scanning transmission electron microscopy, geometric phase analysis, and energy dispersion spectrum, we explored the microscopic mechanism of stabilizing the tail-to-tail charged domain walls with upward center-divergent quad-domain structures in BiFeO3 nanoislands. The comprehensive factors include the fully relaxed rhombohedral phase in nanoislands, negative surface screening charges, and upward built-in bias at the BiFeO3-(La,Sr)MnO3 interface, which are respectively induced by interfacial periodic dislocations, surface reconstructions, and interfacial terminations. Moreover, the unusual polarization state and domain-wall arrangement in the nanoislands were also proved to be stable even at an elevated temperature. [ABSTRACT FROM AUTHOR]

The optic-electronic response is usually limited by poor electron–hole separation and phonon thermalization. Here, we show that natural superlattice materials with charged layers in BiOCuCh (Ch = S, Se, Te) can effectively suppress bulk carrier recombination and dissipation from phonon. The photogenerated hot carriers in BiOCuCh are separated by the intrinsic p–n junction naturally composed of the [Cu2Ch2]2− and [Bi2O2]2+ layers, and transport occurs with high speed within the two layers. Moreover, its dissipation can be substantially reduced because the interlayer coupling leads to low phonon thermalization. As a result, these materials both show prominent response to full-spectrum solar lights and resemble cocatalysts in their characteristics. Because of these merits, these oxychalcogenides provide a penetration point up-and-coming platform for the exploration of materials with an extraordinary optoelectric response. [ABSTRACT FROM AUTHOR]

Ceramic capacitors are ubiquitously used in high power and pulse power applications, but their low energy density, especially at high temperatures (>150 °C), limits their fields of application. One of the reasons is the low energy efficiency under high electric fields and/or at high temperatures. In this work, equimolar Sm3+ and Ti4+ cations were doped in NaNbO3 to increase relaxor characteristics and energy storage properties. The optimal recoverable energy density Wrec of 6.5 J/cm3 and energy efficiency η of 96% were attained in the ceramics with 10% (Sm, Ti) concentration (SmT10). Dense microstructure and low dielectric loss were attributed to the high energy storage performance. Impedance spectra analysis revealed that the grain boundary resistance dominates at low temperatures, while the grain resistance dominates at high temperatures. The ceramics show stable Wrec and η in a broad temperature range of −90 to 200 °C and repeated charge–discharge cycles up to 105. The comprehensive energy storage performance indicates SmT10 ceramics are among potential candidates for ceramic capacitors working at high temperatures. [ABSTRACT FROM AUTHOR]

Dielectric ceramics with high polarization and low sintering temperature are important for high-performance and low-cost multilayer ceramic capacitors (MLCCs). Herein, BiFeO3 was added to a lead-free composition 0.48BaTiO3-0.4Bi(Mg0.5Hf0.5)O3-0.12SrTiO3 to lower the sintering temperature and increase the polarization simultaneously. As a result, a low sintering temperature of 950 °C and high comprehensive energy storage properties with a recoverable energy density Wrec of 5.7 J/cm3 and an energy efficiency η of 92% at 450 kV/cm were achieved. Together with the good temperature stability and cycling stability of Wrec and η, the ceramics exhibit great potential in the energy storage MLCCs with low-cost Ag-Pd electrodes with a high Ag content. [ABSTRACT FROM AUTHOR]

Control of magnetism in multiferroic heterostructures using low-energy consumption is significant both in fundamental physics and for practical applications such as storage or logic devices. Through switching the ferroelectric polarization of the whole BiFeO3 films using an acidic aqueous solution, we studied the deterministic control of exchange coupling and magnetization in BiFeO3/La1 − xSrxMnO3 heterostructures. It is found that the hole concentration of La1 − xSrxMnO3 is closely coupled with BiFeO3 polarization, which can be used to switch the interfacial magnetism. The polarization-determined exchange coupling for the Sr concentration of x = 0.2 is contrary to that of x = 0.33 and 0.5 due to different double exchange strengths, while for x = 0.5, the coupling effects are more sensitive to polarization. This work provides a pathway to control interfacial magnetism and multiferroicity at a large scale using green energy. [ABSTRACT FROM AUTHOR]

Polar topologies in ferroelectric/paraelectric superlattices have been an important substance to explore exotic physical properties. Although enormous efforts have been paid to this field, the universality of the formation of polar topologies in various superlattices and their electric field dynamics is still unknown. Herein, we employ a phase-field model to construct three types of ferroelectric/paraelectric superlattices with tetragonal, rhombohedral, and orthorhombic symmetries and investigate their static structures and dynamic responses as a function of epitaxial strain. It is found that all superlattices undergo a similar vortex–spiral–in-plane topology transition, which corresponds to peaked dielectric permittivity curves and ferroelectric-, antiferroelectric-, and paraelectric-like hysteresis loops. Such polarization behaviors are attributed to the triple-well free energy landscape. The flexibility of hysteresis loops generates high energy density and efficiency of ferroelectric/paraelectric superlattices. This study offers a systematic view of the generality of polar topologies in multilayered ferroelectrics. [ABSTRACT FROM AUTHOR]

Dielectric energy storage capacitors as emerging and imperative components require both high energy density and efficiency. Ferroelectric-based dielectric thin films with large polarizability, high breakdown strength, and miniaturization potential hold promises for competitive integrated and discrete energy storage devices. Since ferroelectric domains are central to polarization hysteresis loops and, hence, energy storage performances, domain engineering has been widely used in dielectric thin films. In this Perspective, we focus on the most state-of-the-art dielectric energy storage films in the framework of domain engineering. Generally applicable domain engineering strategies are overviewed, followed by articulative examples of their implementation in modulating domain sizes and symmetries that enhance the energy storage. Finally, we envision prospects of further improvements of dielectric thin films within domain engineering and beyond. [ABSTRACT FROM AUTHOR]

Iron garnets as an important type of low-damping magnetic insulator can provide an ideal platform for the field of magnonics. In this work, we study the propagation of spin waves in a 60 nm-thick TmIG film with perpendicular magnetic anisotropy using all-electrical spin wave spectroscopy. The magnetostatic forward volume mode spin waves show a fully reciprocal propagation. By sweeping out-of-plane magnetic fields in the low-field regime, spin textures are created and observed; meanwhile, the spin wave mode vanishes, which indicates that propagating spin waves are filtered by the spin textures. By applying a large in-plane field, spin wave propagation in a Damon–Eshbach configuration is studied. Our findings provide a potential method to explore reconfigurable magnonic devices. [ABSTRACT FROM AUTHOR]

The ability to tune magnetic orders, such as magnetic anisotropy and topological spin texture, is desired to achieve high-performance spintronic devices. A recent strategy has been to employ interfacial engineering techniques, such as the introduction of spin-correlated interfacial coupling, to tailor magnetic orders and achieve novel magnetic properties. We chose a unique polar–nonpolar LaMnO3/SrIrO3 superlattice because Mn (3d)/Ir (5d) oxides exhibit rich magnetic behaviors and strong spin–orbit coupling through the entanglement of their 3d and 5d electrons. Through magnetization and magnetotransport measurements, we found that the magnetic order is interface-dominated as the superlattice period is decreased. We were able to then effectively modify the magnetization, tilt of the ferromagnetic easy axis, and symmetry transition of the anisotropic magnetoresistance of the LaMnO3/SrIrO3 superlattice by introducing additional Mn (3d) and Ir (5d) interfaces. Further investigations using in-depth first-principles calculations and numerical simulations revealed that these magnetic behaviors could be understood by the 3d/5d electron correlation and Rashba spin–orbit coupling. The results reported here demonstrate a new route to synchronously engineer magnetic properties through the atomic stacking of different electrons, which would contribute to future applications in high-capacity storage devices and advanced computing. [ABSTRACT FROM AUTHOR]

ZnO hexagonal bipods have been synthesized by a hydrothermal method using NaAOT as template. Co-doped ZnO bipods show obvious room temperature ferromagnetic behaviours. Phase composition, microstructure, and x-ray photoemission spectra analysis indicate that there is no Co cluster exsisting in the samples, and the ferromagnetism observed in Co-doped ZnO bipods should be intrinsic. Photoluminescence spectra indicate there exist a large amount of oxygen vacancies in the ZnO bipods. The ferromagnetism can be tuned by the content of Co ions, which should be closely realted to the magnetic coupling interaction between the Co2+ 3d spins and the electrons trapped at oxygen vacancies. [ABSTRACT FROM AUTHOR]

Ca and Mn co-doped BiFeO3 (BFO) thin films were fabricated on (111) Pt/Ti/SiO2/Si substrates via a simple solution approach. Enhanced ferroelectric properties were obtained in these Ca and Mn co-doped BFO films, e.g., large remnant polarization value (Pr ∼ 89 μC/cm2) and large remnant polarization to saturated polarization ratio (Pr/Ps ∼ 0.84) for Bi0.90Ca0.10Fe0.90Mn0.10O3 film. X-ray diffraction and Raman spectra of these films showed that B-site Mn doping causes substantial structural transition toward orthorhombic phase and A-site Ca doping facilitates an evolution to tetragonal phase with higher crystal symmetry. The structural transitions are in favor of enhanced ferroelectric properties in the BFO films. The approach of A and B site co-doping is proved to be effective in enhancing ferroelectric performance in multiferroic BFO films. [ABSTRACT FROM AUTHOR]

(100)-oriented Pb0.97La0.02(Zr0.95Ti0.05)O3 (PLZT) antiferroelectric films with a thickness of about 1.7 μm were deposited on Pt-buffered silicon substrates via a sol-gel process. The room-temperature capacitance density of the films was above 195 nF/cm2 over the frequency range from 1 kHz to 1 MHz. The recoverable energy density was enlarged with increasing measurement field, and a maximum value of 12.4 J/cm3 at 1120 kV/cm was obtained at room temperature. From the temperature-dependent electric-field-induced polarization hysteresis loops, a maximum reversible adiabatic temperature change, ΔT = 8.5 °C, was obtained near the phase-transition temperature. [ABSTRACT FROM AUTHOR]

Microscale 1-3-type-like magnetoelectric (ME) composites with ferromagnetic microstrips laterally embedded in a piezoelectric ceramic substrate were fabricated by a dice-and-insert method. Mechanically sliced microstrips of Li/Ta-modified (K,Na)NbO3 lead-free ceramics and CoFe2O4 ceramics were used as the piezoelectric and piezomagnetic phases, respectively, which were inserted into each other and bonded together by epoxy. The ME properties of such 1-3-type-like composites with piezoelectric substrates were verified. The maximum ME coefficient was found to vary with the strip size, substrate thickness, and thickness of epoxy bonding layers. A maximum value of 48 mV/(cm·Oe) was achieved. In addition, a special anisotropy was obtained in the present lateral 1-3 type ceramic composites and made it have potential applications in detecting magnetic field directions. [ABSTRACT FROM AUTHOR]

Polycrystalline NiO-based thin films with Li or/and transition metal ions (V, Cr, Mn, Fe, Co, Cu, Zn) doping have been prepared by a sol-gel spin-coating method. Magnetization measurements reveal that V-, Fe-, and Mn-doped NiO thin films show obvious room-temperature ferromagnetic behaviors and ferromagnetic properties can be enhanced by the Li co-doping. Microstructure and X-ray core-level photoemission spectra analysis indicate that the ferromagnetism was not from the impurity TM metal cluster and may be ascribed to double exchange coupling effects via Li-induced holes. [ABSTRACT FROM AUTHOR]

Bi0.95A0.05FeO3 (A = Ba, Sr, Ca) thin films were deposited on (111) Pt/Ti/SiO2/Si substrates via chemical solution deposition. The magnetization of the doped specimens increases sharply as compared to that of pure BiFeO3, and it increases as the doped ionic radius gets larger. X-ray diffraction analysis reveals that the films are single phase, and no other extra magnetic phases are detected. X-ray photoelectron spectroscopy analysis suggests that the content of Fe3+ increases and that that of Fe2+ decreases. According to the x-ray diffraction and Raman analyses, there are corresponding changes in the lattice parameters and the Raman spectra as the doped ionic radius gets larger. These results indicate that neither the magnetic coupling of Fe2+ nor the parasitic magnetic phases could be the origin of the magnetization improvement, and we consider that the magnetization improvement mainly originates from the doped ionic radius size effect. [ABSTRACT FROM AUTHOR]

We prepared La doped of CaCu3Ti4O12 ceramics by a solid-state sintering process and observed nonlinear electrical varistor and high dielectric behaviors. Phase composition analyses show that the La can substitute on the Ca sites completely, and have no influence on the phase composition. The impedance spectroscopy at room temperature indicates that the La doping can maintain the dielectric permittivity of CaCu3Ti4O12 (∼104). The relationships between electrical current density versus applied electrical field show that these ceramic samples exhibit nonlinear varistor characteristics, which should be ascribed to the existing potential barrier height at the grain boundary. [ABSTRACT FROM AUTHOR]

Anatase titania-coated bismuth ferrite nanocomposites (BiFeO3/TiO2) have been fabricated via a hydrothermal approach combined with a hydrolysis precipitation processing. Analysis of the microstructure and phase composition reveals that a core-shell BiFeO3/TiO2 structure can be formed, which results in a significant redshift in the UV-vis absorption spectra as compared to a simple mechanical mixture of BiFeO3–TiO2 nanopowders. The core-shell structured BiFeO3/TiO2 nanocomposites exhibit higher photocatalytic activity for photodegradation of Congo red under visible-light (λ>400 nm) irradiation, which should be attributed to the enhancement of the quantum efficiency by separating the electrons and holes effectively. The obtained BiFeO3/TiO2 nanocomposites can be used as potential visible-light driven photocatalysts. [ABSTRACT FROM AUTHOR]

BiFeO3 films of different thicknesses were grown on the LaNiO3-buffered Si (100) substrate via a sol-gel spin-coating processing. X-ray diffraction and Raman spectra studies revealed a thickness dependent structural and strain state evolution. The thickness dependent size effect on ferroelectric behavior was reflected in the polarization versus electric field hysteresis loops and domain structures. Enhancement in magnetization of the thin BiFeO3 films resulted from the strain-induced canting antiferromagnetic structure, and remarkable anisotropy was observed in the 40 nm BiFeO3 film as well due to the magnetoelastic effect induced by strain. With the increase in the film thickness, the magnetic moment of BiFeO3 films decreased back to the ordinary canted antiferromagnetic state. [ABSTRACT FROM AUTHOR]

Site modification in BiFeO3 films was investigated using Raman spectroscopy and piezoelectric force microscopy to explore effect of A- and B-site modifications on structural evolution and ferroelectric behavior of doped BiFeO3 films. Our Raman results revealed the subtle structural changes in the BiFeO3 films caused by the changes of the short-range force in the crystal lattice induced by ionic radii mismatch. The observation of ferroelectric domain and the control of domain switching through an electric field in these doped BiFeO3 films were realized by piezoelectric force microscopy. Piezoelectric response of these doped BiFeO3 films illustrated dependence of their properties upon the lattice symmetry and film microstructure. [ABSTRACT FROM AUTHOR]

We prepared TiO2-rich CaCu3Ti4O12 (CCTO) ceramics by a solid-state sintering process and observed large nonlinear electrical and high dielectric behaviors. Microstructure and phase composition analyses show that CCTO grain-amorphous/TiO2 nanograin boundary-CCTO grain junction structures exist in these TiO2-rich CCTO ceramics, which leads to the nonlinear electrical and high dielectric properties. The temperature dependence of impedance spectroscopy and relationships between electrical current density versus applied electrical field indicate that the activation energy of the grain boundary for the TiO2-rich CCTO ceramics is almost the same as the potential barrier height and both of them are weakly independent of the doped concentration of TiO2, which supports the internal barrier layer capacitor model of Schottky barriers at the grain boundaries between semiconducting CCTO grains. [ABSTRACT FROM AUTHOR]

Multiferroic magnetoelectric materials, which simultaneously exhibit ferroelectricity and ferromagnetism, have recently stimulated a sharply increasing number of research activities for their scientific interest and significant technological promise in the novel multifunctional devices. Natural multiferroic single-phase compounds are rare, and their magnetoelectric responses are either relatively weak or occurs at temperatures too low for practical applications. In contrast, multiferroic composites, which incorporate both ferroelectric and ferri-/ferromagnetic phases, typically yield giant magnetoelectric coupling response above room temperature, which makes them ready for technological applications. This review of mostly recent activities begins with a brief summary of the historical perspective of the multiferroic magnetoelectric composites since its appearance in 1972. In such composites the magnetoelectric effect is generated as a product property of a magnetostrictive and a piezoelectric substance. An electric polarization is induced by a weak ac magnetic field oscillating in the presence of a dc bias field, and/or a magnetization polarization appears upon applying an electric field. So far, three kinds of bulk magnetoelectric composites have been investigated in experimental and theoretical, i.e., composites of (a) ferrite and piezoelectric ceramics (e.g., lead zirconate titanate), (b) magnetic metals/alloys (e.g., Terfenol-D and Metglas) and piezoelectric ceramics, and (c) Terfenol-D and piezoelectric ceramics and polymer. The elastic coupling interaction between the magnetostrictive phase and piezoelectric phase leads to giant magnetoelectric response of these magnetoelectric composites. For example, a Metglas/lead zirconate titanate fiber laminate has been found to exhibit the highest magnetoelectric coefficient, and in the vicinity of resonance, its magnetoelectric voltage coefficient as high as 102 V/cm Oe orders has been achieved, which exceeds the magnetoelectric response of single-phase compounds by many orders of magnitude. Of interest, motivated by on-chip integration in microelectronic devices, nanostructured composites of ferroelectric and magnetic oxides have recently been deposited in a film-on substrate geometry. The coupling interaction between nanosized ferroelectric and magnetic oxides is also responsible for the magnetoelectric effect in the nanostructures as was the case in those bulk composites. The availability of high-quality nanostructured composites makes it easier to tailor their properties through epitaxial strain, atomic-level engineering of chemistry, and interfacial coupling. In this review, we discuss these bulk and nanostructured magnetoelectric composites both in experimental and theoretical. From application viewpoint, microwave devices, sensors, transducers, and heterogeneous read/write devices are among the suggested technical implementations of the magnetoelectric composites. The review concludes with an outlook on the exciting future possibilities and scientific challenges in the field of multiferroic magnetoelectric composites. [ABSTRACT FROM AUTHOR]

Bilayered multiferroic nanocomposite films of preferentially oriented Pb(Zr0.52Ti0.48)O3 (PZT) and CoFe2O4 (CFO) were prepared on general Pt/Ti/SiO2/Si substrate via a simple solution processing. Different annealing processings resulted in different preferential orientations for the PZT layers in the bilayered thin films, on which the dependence of properties, including ferroelectric, ferromagnetic, and magnetoelectric properties, in the PZT-CFO nanocomposite thin films was investigated. Strong ferroelectric and ferromagnetic responses and, in particular, direct magnetoelectric coupling effect were simultaneously observed in these bilayered thin films at room temperature. [ABSTRACT FROM AUTHOR]

The effect of Tb doping on crystal structure and electric and magnetic behavior of BiFeO3 thin films prepared via a solution processing on (111)Pt/Ti/SiO2/Si substrates was studied. The substitution of Bi ions by a small amount of Tb ions could stabilize the valence of Fe3+ in BiFeO3 thin films, and as indicated by transmission electron microscope images and largely reduced leakage current in comparison with pure BiFeO3 thin films, the quality of the films was improved by Tb doping. Electric and magnetic behavior of Tb-doped BiFeO3 films was investigated with employing La-doped BiFeO3 films as comparison. Large enhancement in both remnant and saturation polarization and the polarization switching were observed in Tb-doped BiFeO3 films, while the inhomogeneous spin-modulated magnetic structure of BiFeO3 was not modified through Tb substitution but by La substitution. [ABSTRACT FROM AUTHOR]

A simple epitaxial heterostructure of NiFe2O4–BaTiO3 grown on (001)-SrTiO3 substrate was prepared via pulsed laser deposition. Structural characterization by x-ray diffraction and electron microscopy showed good horizontal heterostructure of (001)-NiFe2O4∥(001)-BaTiO3 epitaxially grown on the substrate, which presents simultaneously strong ferroelectric and ferromagnetic responses at room temperature. In particular, an obvious direct magnetoelectric coupling was observed in the heterostructured film, which provides a convincing measurement of the direct magnetoelectric effect in the multiferroic nanostructures. [ABSTRACT FROM AUTHOR]

In exploring approaches to enhance ionic conductivity of solid polymer electrolytes, adding inert fillers has proved to be effective. In the present work, by doping ionically active SiO2 particles, which were designed by absorbing and confining liquid plasticizers in the nanosized pores of SBA-15 (a kind of mesoporous SiO2) to the polyethylene oxide (PEO)-LiClO4 matrix, about 10-fold further enhancement in the ionic conductivity was achieved as compared with adding inert SBA-15. The fillers dispersed homogenously in the PEO matrix. The ambient ionic conductivity reaches about 1.5×10-4 S cm-1 for (PEO)8-LiClO4/10 wt % active SBA-15 films. Moreover, other properties such as the ambient lithium transference number, long-term stability of bulk and lithium metal electrode/electrolyte interfacial resistance, and the electrochemical window also showed good results. Application of such electrolytes in lithium batteries was asserted by cell testing with LiCoO2 cathode and lithium metal anode. [ABSTRACT FROM AUTHOR]

Magnetoelectric resonance behavior of a simple, bilayered structure of Pb(Zr,Ti)O3 ceramic chip and (Tb,Dy)Fe2/epoxy mixture layer is investigated. Our results show that there occur three kinds of resonance, which are attributed to the first-order flexural, second-order flexural, and radial resonance modes, respectively. The measured phase spectra show a significant phase change around each resonance frequency. The thinner PZT chip is benefit for higher flexural resonance magnetoelectric effect. The magnetoelectric effects measured under open and short electric boundary conditions show different behaviors. This simple bilayered structure exhibits a large charge output of about 300 pC/Oe at the resonance frequency. [ABSTRACT FROM AUTHOR]

Multiferroic laminated composites of PbZr0.52Ti0.48O3(PZT)/CoFe2O4(CFO)/PbZr0.52Ti0.48O3 were prepared by conventional ceramic processing. The interdiffusion of the elements between different layers occurred, altering material properties. The dielectric behavior of such a sandwiched ceramic was dominated by the relative thickness of the different layers because of the high dielectric constant of the PZT layer and the low dielectric constant of the CFO layer. The magnetoelectric behaviors were strongly dependent on the relative thickness of the CFO layer, dc magnetic field, ac magnetic frequency, and the angle θ between the magnetic field and polarization direction. The maximal magnetoelectric-induced voltage coefficient of the composites reaches up to about 27 mV/Oe, close to what was reported previously. The magnetoelectric effect of the laminated composites was also simulated with the finite-element method. The reasons for the difference between experiment and simulation were discussed. [ABSTRACT FROM AUTHOR]

The solute-drag-dependent growth kinetics of core-shell-structured grains in rare-earth-doped BaTiO3 ceramics was studied based on an analytical description of the diffusion of rare-earth atoms doped. Dependence of the sizes of grain core and shell on the sintering conditions, dopant content, and starting powder size was quantitatively revealed. The effective dielectric constant of the ceramics was calculated in terms of the relative contents of the ferroelectric core and paraelectric shell. The calculations are in good agreement with the experimental observations. [ABSTRACT FROM AUTHOR]

A micromechanics method is developed for the effective magnetostrictive behavior of magnetostrictive composite materials. Explicit relations for determining the effective magnetostriction of the particulate composites with cubic magnetostrictive crystallites are derived and reduce to the well-known results in the case of simple polycrystals with elastically isotropic magnetostrictive crystallites. Numerical calculations for the effective saturation magnetostriction of SmFe[sub 2]/Fe or Al, and Terfenol-D/epoxy composites show that the theoretical estimates correlate well with experimental data, and they also show the interesting magnetostrictive behavior of the composites. [ABSTRACT FROM AUTHOR]

Discusses a study which presented the direct current (dc) electrical properties and alternating current impedance spectra of presintered compacts of nanocrystalline (NC) zinc oxide (ZnO) having various grain sizes. Experimental procedure of the study; Identification of anomalous dc conductive currents; Result of the impedance spectroscopy.

Nanoscale magnetism in oxides with the lateral size down to 300 nm is critical for scientific investigation and advanced technological applications such as spintronics, but often complicated to fabricate. Specifically, the emergent magnetic phenomena induced by the size effect attract tremendous attention. In this situation, fabrication of self-assembled nanoarchitectures in complex oxides and strategically modulating their properties are urgently needed. Here, we report the emerging single ferromagnetic phase state in self-assembled nanowires on the thin film surface of mixed valence manganite La0.5Sr0.5MnO3, by using low temperature magnetic force microscopy. The ferromagnetic state can be reversely switched in the presence of an external magnetic field. This work paves the way for manipulating the phase coexistence state without an external field and provides insight into the size limitation for designing next generation electronic and spintronic devices in complex oxide systems. [ABSTRACT FROM AUTHOR]

Different layered perovskite-related oxides are known to exhibit important electronic, magnetic, and electrochemical properties including metal-insulator transition, colossal magnetoresistance, excellent mixed ionic/electronic conductivity, and especially their flexible tunability by external or internal stimuli. Here, we show that the microstructure and magnetic properties of double perovskite PrBaMn2O5.5+δ (PBMO) epitaxial films can be co-tuned by the physical strain via a proper choice of substrate and film thickness and the chemical strain from the concentration of oxygen vacancies. It is surprisingly found that the films with more oxygen vacancies reveal more Mn4+ formed along with Mn2+ under the influence of interface strain, and meanwhile, Mn4+ exhibits a thickness-dependent distribution with a high amount at the interface. Consequently, the increased proportion of Mn4+ diminishes the saturation magnetization and decreases the Curie temperature of PrBaMn2O5.5+δ epitaxial films, revealing the availability of physical and chemical strains tuning the properties of highly epitaxial double perovskite films. [ABSTRACT FROM AUTHOR]

Magnetoelectric effect enables controlling magnetism with an electric field or controlling polarization remotely with a magnetic field, without involving any driving electric currents. Since its discovery in the 1960s, the magnetoelectric effect has constantly been inspiring new fundamental science and the development of fascinating device concepts. This perspective is focused on two types of magnetoelectric devices: an ultralow-heat-dissipation spin memory/logic and a magnetoelectric magnetic field sensor. For each device, the paper first overviews the potential market needs, then discusses several key device attributes and outstanding challenges. An outlook for the development of other magnetoelectric devices is also provided. [ABSTRACT FROM AUTHOR]

A methodology is introduced for predicting the effective thermal conductivity of arbitrary particulate composites with interfacial thermal resistance in terms of an effective medium approach combined with the essential concept of Kapitza thermal contact resistance. Results of the present model are compared to existing models and available experimental results. The proposed approach rediscovers the existing theoretical results for simple limiting cases. The comparisons between the predicted and experimental results of particulate diamond reinforced ZnS matrix and cordierite matrix composites and the particulate SiC reinforced Al matrix composite show good agreement. Numerical calculations of these different sets of composites show very interesting predictions concerning the effects of the particle shape and size and the interfacial thermal resistance. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Proposes an effective-medium theory to treat coupled electromechanical behavior in composite media. Expression for the coupled interaction between the electric and elastic variables; Numerical results of piezoelectric composites; Discussion on the critical behavior in piezoelectric material.

Nanostructured BiFeO3 particles have been synthesized by a hydrothermal method, and the effects of particle size on photocatalytic activity and magnetic property of BiFeO3 were investigated. The optical absorption spectra indicate that the band-gap energy increases with decreasing crystalline size due to the quantum-size effect. The enhancement of room-temperature weak ferromagnetism can be observed in nanoscale BiFeO3 particles, which should be attributed to the size-confinement effect on the magnetic ordering. In addition, BiFeO3 nanoparticles with diameter about 5 nm show good photocatalytic performance by photodegradation of Congo red under visible-light (λ>400 nm) irradiation. [ABSTRACT FROM AUTHOR]

Mn-doped BaTiO3 nanoparticles have been synthesized using a hydrothermal method. Phase composition, microstructure, and Raman spectroscopy analysis indicate that a double-phase structure containing both cubic and tetragonal structures can be obtained. Electron paramagnetic resonance and x-ray photoelectron spectroscopy measurements prove that Mn ions exist as a form of Mn2+ in these nanoparticles. Magnetization measurements reveal that a ferromagnetic behavior can be observed in the Mn-doped BaTiO3 at low temperature, and the nominal ratio of Ba/Ti has a great influence on the ferromagnetic properties. This ferromagnetic mechanism can be ascribed to the exchange coupling interaction between the Mn2+ ions and the Ti4+ vacancy. [ABSTRACT FROM AUTHOR]

It has been known that ferroelectric charged domain walls (CDWs), which break the polarization continuity, may be electrically active with an elevated conductivity. However, the bound charge at CDWs may render them energetically unstable, and thus, forming CDWs naturally and manipulating them electrically is still challenging. Here, we theoretically utilize phase-field simulations to design spontaneously generated CDWs with center-type quad-domains in a single square-shaped BiFeO3 nanoisland. It is shown that the stability of the spontaneously emerging head-to-head domain walls with center-convergent quad-domains is mainly determined by three contributions, namely, the geometrical constraint from approximately 45°-tilted bottom edges, the electric boundary condition, and the necessary screening free charges to compensate head-to-head domain walls. It is demonstrated that the center-convergent quad-domains with head-to-head CDWs can be electrically switched to the center-divergent one with tail-to-tail CDWs, providing guidance for achieving ferroelectric domain-wall-based nanodevices with low-power dissipation. [ABSTRACT FROM AUTHOR]

The Li-doped Ni–Si–O thin films (LixNi0.90-xSi0.10O, x=0.0–0.05) have been prepared by a sol-gel spin-coating method on silicon and quartz glass substrates. Analysis of phase composition and microstructure indicates that the films consist of cubic NiO phase and amorphous phase as annealed at 700 °C for 5 min. With the Li-doping concentration increasing, the core-level photoemission spectra show that a loss of the double-peak structure of the Ni 2p3/2 main line can be observed and current density of the films increases greatly, which should be ascribed to the increase of the hole carriers induced by the Li doping. Ultraviolet-visible absorption spectra indicate that the absorption edge of the films exhibits a redshift due to the related defects. [ABSTRACT FROM AUTHOR]

Strain effects on domain structures and thermal stability in single-domain magnetic thin films were studied using thermodynamic analysis. The strain-domain structure and stability diagrams were established and compared to several existing experimental results. The structure diagram displays various stable single-domain states under in-plane normal and/or in-plane shear strains by minimizing the free energy density whereas the stability diagram takes into account possible thermal excitations and hence illustrate the thermally stable magnetic single-domain states. The results improve the understanding of strain-magnetization correlation in magnetic thin films and provide useful insight for the development of strain-engineered magnetic nanostructures with novel functionalities. [ABSTRACT FROM AUTHOR]

The low power factor (PF) of BiCuSeO oxyselenide inhibits further improvement on thermoelectric figure of merit in the moderate temperature range. In this Letter, we show that the electron transport properties of doped BiCuSeO oxyselenide can be accurately described in acoustic phonon scattering assumption within the framework of single parabolic band model. It is further found that the doping elements alter the electron transport properties by tuning the effective mass and deformation potential. Based on these understandings, we argue that the higher power factor can be achieved by choosing the doping element based on reducing deformation potential coefficient and decreasing effective mass. [ABSTRACT FROM AUTHOR]

Comments on the method for predicting the coupled magnetoelectric effect in piezoelectric-piezomagnetic composite containing ellipsoidal inclusions. Series of interrelations between moduli for a uniaxially aligned long fiber composite; Coupled magnetoelectric effect based on equivalent inclusion method.

Erratum: "Spin wave propagation in a ferrimagnetic thin film with perpendicular magnetic anisotropy" [Appl. Phys. The field is swept from -35 to 35 mT with a step of 1 mT. (b) A spin-wave spectrum extracted from (a) at -10 mT. (c)-(f) show the Magnetic Force Microscopy scanning image at 5, 9, 11, and 13 mT, respectively. The scale bar is 1 m. The size of the MFM images (c)-(f) is fixed at 5 m ×5 m. The authors apologize for this oversight. [Extracted from the article]