Relaxor ferroelectrics are an important class of functional materials because of their highly tunable dielectric permittivity, excellent temperature stability and low coercive field. However, the phase transition behaviors in relaxor ferroelectrics are very complex near the morphotropic phase boundary (MPB), especially under multiple fields of electric field and temperature. This study investigates the complex phase evolution of Pb(Mg[Formula: see text]Nb[Formula: see text]O3–28%PbTiO3 (PMN–28PT) single crystals near the MPB under thermal and electric field stimuli. Through comprehensive temperature-dependent characterization of the dielectric response, we observe the broad dielectric relaxation, which is attributed to the polar nanoregions (PNRs), as directly visualized via scanning transmission electron microscopy (STEM). The temperature-dependent P–E loops and S–E loops reveal the reduction in polarization magnitude and coercive field, increasing loop symmetry with temperature. Apart from that, a comparative study with conventional ferroelectric BaTiO3 (BTO) reveals that PMN–28PT maintains thermal polarization retention. These findings provide new insights into the structure–property relationships governing relaxor behavior near MPB compositions.

Magnetic properties of OH--intercalated Ni2+-Fe3+ layered double hydroxides (LDH) with a nickel-to-iron ratio (n) of 2 and 3, prepared using two independent synthesis methods, have been studied using the macroscopic magnetic method (SQUID magnetometry) and local-scale element-specific techniques (synchrotron-radiation-based soft X-ray XAS and XMCD). It was revealed that synthesis of NinFe-OH LDH using either coprecipitation or urea-based hydrothermal methods was accompanied by formation of small amounts of nanosized (on the order of 4-5 nm) particles of Ni2FeO4 and α-Fe2O3, respectively. Comparative analysis of static and dynamic magnetic response allowed us to extract the contribution of the impurity phases to the total magnetic response of the prepared samples and refine the intrinsic magnetic behavior of the studied NinFe-OH LDH. The extracted true field-dependent magnetic behavior of Ni2Fe-OH LDH prepared using two independent synthesis routes was revealed to differ, indicating possible clusters of long-range Ni/Fe cation ordering in material produced via the urea-based method. In all studied compositions, the features that indicate a glassy magnetic state at low temperatures were observed. This behavior is suggested to result from competing antiferromagnetic and ferromagnetic metal-oxygen-metal interactions with Ni2+ and Fe3+, which occur in nanosized and morphologically anisotropic LDH crystallites.

In response to the increasing demand for efficient and compact refrigeration and energy conversion devices, research has focused on identifying optimal electrocaloric (EC) materials among ferroelectric ceramics and polymers. This study investigates the EC properties of the Poly [(Vinylidene Fluoride)0.664-(Trifluoroethylene)0.245-(Chlorofluoroethylene)0.091] terpolymer and multi-layer Ba0.6Sr0.4Ti0.998Mn0.002O3 (BSTM) ceramics, comparing various parameters to assess their suitability for advanced energy applications.The multilayer ceramic capacitor contains a large amount of inactive material, which hinders the performance of the capacitor both in terms of zTad and efficiency. Finite-element modeling with direct temperature measurement was therefore employed to extract intrinsic electrocaloric response from geometric and diffusion effects, providing the zTad and diffusion-related energy losses required for evaluating the cooling efficiency. Adiabatic temperature change (zTad) obtained in an electric field representing long-term operation, reaches 4.91 degrees C for Terpo at 100 V/ & micro;m and 3.0 degrees C for BSTM at 30 degrees C. The loss in ferroelectric hysteresis is observed to be much lower in BSTM than in PVDF Terpolymer. Hence, the cooling efficiency relative to Carnot reveals that the PVDF Terpolymer achieves a relative cooling efficiency upper bound of 4.5% at 100 V/& micro;m, whereas BSTM ceramics reach nearly 14 times, being 62.1% at 30 V/& micro;m. The PVDF Terpolymer outperforms BSTM ceramics in terms of adiabatic temperature change and flexibility, but not in terms of expected cooling efficiency. Considering these complementary strengths, both BSTM ceramics and PVDF terpolymers emerge as promising electrocaloric materials for advanced energy applications, including solid-state cooling and energy harvesting.

As promising candidates for next-generation energy storage devices in electrical and electronic systems, lead-free multilayer ceramic capacitors face increasingly high performance requirements. To counteract the usual trade-off between energy storage density and efficiency, we here propose a high-entropy design that directly harnesses diverse oxide symmetries to targetedly engineer competing orders and tune the composition into the crossover region between relaxor ferroelectric and superparaelectric states. Atomic-scale structural analysis reveals high-entropy ceramic develops pronounced local polarization fluctuation and dispersed oxygen octahedral rotations, which enhance relaxor behavior and reduce switching barrier. Consequently, superior recoverable energy density of 20.64 J cm-3 and high efficiency of 94.2% are obtained in our designed high-entropy Bi0.5Na0.5TiO3-based multilayer ceramic capacitors, along with excellent thermal/anti-fatigue stability and charge-discharge capabilities. This work provides a transferable strategy to engineer competing orders in lead-free dielectric materials and successfully achieves high-entropy multilayer ceramic capacitors with superior energy storage performance.

Magnetoelectric multiferroics are foreseen as paramount materials to control magnetism with an electric-field, targeting energy-efficient spintronics. The archetypal room-temperature antiferromagnetic ferroelectric, BiFeO3, harbors an incommensurate antiferromagnetic cycloid whose propagation direction is locked to ferroelectric domains. Epitaxial strain was shown to affect this antiferromagnetic ordering, stabilizing different cycloidal propagation directions, or a collinear antiferromagnetic state. Here we demonstrate the reversible, nonvolatile, electric-field triggered magnetic phase transition between two distinct antiferromagnetic states at room temperature. Using SrTiO3 vicinal substrates, we stabilize a single ferroelectric domain associated with a single antiferromagnetic cycloidal state in BiFeO3 epitaxial thin films. Electrically reversing the ferroelectric polarization deterministically within the same ferroelastic domain induces a reversible transition from a cycloidal to a collinear antiferromagnetic state, as directly visualized by scanning nitrogen vacancy (NV) magnetometry. These results bring insights into magnetoelectric devices for ultrafast and low-power spintronics.

When the size of ferroelectric materials is reduced to the nanoscale, novel phenomena emerge from the interplay of electrostatic, strain, surface, defect, and confinement effects, offering exciting opportunities for applications in nanoelectronics, optoelectronics, and biomedicine. Despite extensive studies on the model ferroelectric BaTiO3, a clear understanding of how synthesis routes govern the relationships among structure and functional properties in BaTiO3 nanoparticles remains lacking. In this work, BaTiO3 nanoparticles were synthesized via coprecipitation, chemical bath precipitation, and hydrothermal method based on the hydrolysis-condensation-nucleation mechanism, and their microstructure, electrical and optical properties were characterized. To further achieve tunable luminescence and probe local structure–property relationships, Er3+ ions were introduced as luminescent centers and their photoluminescence behavior was analyzed. The coprecipitated BaTiO3 nanoparticles exhibit smaller particle size, higher surface area and increased local defect density, which favor surface-mediated catalytic processes. In contrast, the chemical bath precipitated sample shows pronounced rare-earth-mediated emission, highlighting its potential for bioimaging and nanomedicine applications. The hydrothermally synthesized BaTiO3 nanoparticles demonstrate enhanced ferroelectric polarization, a multidomain texture, and a reduced band-gap energy, rendering them promising for optoelectronic device applications.

We investigate the interplay between strain and magnetism in Ce2Fe17 using first-principles calculations, focusing on its response to biaxial deformation in the (ab) plane. Our results show a piezomagnetic, i.e., linear, variation of the magnetization over the range +/- 2% applied to the in-plane area (corresponding approximately to +/- 1% on the lattice vectors). Quantitatively, we obtain A(eff )approximate to -10.4 & times; 10(-6) T-1 and A(int) approximate to -12.5 & times; 10(-6) T-1. Site-resolved analysis shows that Fe(18h) and Ce sites dominate the absolute and relative moment changes. We interpret the increase in magnetization with increasing tensile strain as resulting from a higher localization of Fe 3d and Ce 4f electrons caused by the increase in interatomic distance of in-plane Fe-Fe bonds, as revealed by the narrowing of their respective bands in the density of states. The spin polarization at the Fermi level increases from 32% to 56% under tensile strain, indicating that the spintronic properties of Ce2Fe17 may be significantly tuned. In the stable ferrimagnetic FM state, the magnetocrystalline anisotropic energy MAE is easy-plane (K-1 < 0) and |K-1| (hence & micro;H-0(a)) increases under tension. Overall, the response reflects a delicate balance between magnetism and structural deformation, emphasizing the role of strain as a tuning parameter for magnetic phases in Ce2Fe17 and related rare-earth intermetallics.

Two-dimensional (2D) Ruddlesden–Popper (RP) perovskites have emerged as stable and tunable alternatives to three-dimensional (3D) perovskites, offering strong excitonic behaviour and improved environmental stability. However, phase-pure formamidinium-based (FA+-based) 2D single crystals, particularly those incorporating a bulky phenylethylammonium (PEA+) spacer, remain difficult to obtain due to rapid nucleation and preferential formation of n = 1 phases. Here, we report a mild solution-growth method that yields millimetre sized (PEA)2(FA)Pb2I7 (n = 2) with well-defined morphology and low defect density. Single crystal X-ray studies reveal a triclinic P1 phase, while X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy verify the chemical composition and purity. The crystals exhibit a direct band gap of 2.18 eV and a narrow photoluminescence peak (PL) at 580.4 nm, indicating efficient radiative recombination. Temperature-dependent PL uncovers a red-shift in the band gap at high temperature, two-regime electron–phonon coupling driven by the thermally activated dynamics of the PEA+ cations. Ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy estimate the band structure of the crystals, with a conduction band minimum value of −3.84 eV and a valence band maximum value of −6.02 eV. These results demonstrate a reliable route for obtaining high-quality FA-based 2D single crystals and provide detailed insights into structural and optical properties, highlighting their potential for next-generation light-emitting and photovoltaic technologies.

The substitution of bismuth by samarium in BiFeO3 is known to induce a structural phase transition from the polar phase to a non-polar phase, with a possible antiferroelectric intermediate structure. In this paper, we investigate the impact of this phase change on the optical properties. The optical bandgap was measured by diffuse reflectance as a function of temperature for several samarium concentrations across the structural phase transition. We found that the optical bandgap for each of the pure phases varies linearly with temperature and that the phase transitions are revealed by smooth transitions between those linear regimes. This allows us to quantify the contribution of the structural change in the optical absorption. We find that a difference in optical bandgap of about approximate to 130 meV can be attributed to the phase change. We anticipate that the same change could be obtained by applying an electric field in an antiferroelectric composition. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

We investigate how the ferroelectric domains of two single-crystal BaTiO3 (BTO) substrates, oriented along [001] and [111], influence the Raman response of monolayer graphene at varying temperatures. A Raman band around 1445 cm−1, close to the G mode and associated with BTO polarization, enables the simultaneous analysis of charge density in graphene and the organization of ferroelectric domains. Raman mapping reveals a periodic modulation in the frequency of graphene's 2D band, correlated with the BTO polarization-related Raman band for both substrate orientations. This effect is more pronounced for BTO (001), which exhibits strong out-of-plane polarization, whereas it is attenuated for BTO (111) due to polarization deviation. The interaction induces spatial charge variations and p–n junction formation in graphene on BTO (001) at room temperature. The periodic modulation effects vanish above the ferroelectric–paraelectric transition (430 K) for both substrates but reappear upon cooling only for graphene on BTO (111). Upon cooling, the BTO [001]-oriented substrate exhibits an emergent distribution of in-plane-oriented ferroelectric domains, eliminating its influence on the Raman mappings of graphene. This emergent distribution is confirmed by Raman mapping of different bands of the BTO [001] single crystal.

Highly sensitive negative temperature coefficient (NTC) thermistors were developed using innovative and stable materials, including perovskites. This study explored the application of bismuth ferrite nanoparticles doped with 6 % neodymium in thermistors. These nanoparticles were synthesized using the Sol-gel method. X-ray diffraction analysis suggests that the Nd0.06Bi0.94FeO3 NPs materials have a rhombohedral structure with an R3c space group. The crystallite sizes were determined using Scherrer's equation, yielding values of approximately 52 nm. Furthermore, the morphological characterization was performed through SEM and TEM analysis, revealing the formation of well-defined grain nanoparticles with an average size of 195 nm. Semi-quantitative energydispersive spectroscopy (EDS) analysis confirmed the presence of the anticipated elements Bi, Fe, Nd, and O, while no secondary elements were detected. The Raman analysis confirmed the structural stability of the Ndmodified BiFeO3 nanoparticles. By studying the dielectric properties, the prepared material showed a negative temperature coefficient of resistance (NTCR) across various temperatures. Calculations of the thermistor constant ((3) and sensitivity factor (alpha) confirmed its suitability as an NTC thermistor.

Cold sintering of perovskite materials is still, despite years of research, challenging. The key objective when coldsintering oxide materials is finding an appropriate liquid phase that triggers pressure-dissolution process and mechano-chemical compaction and densification of ceramics. In this study, cold sintering of the multiferroic BiFeO3 perovskite is reported for the first time. When organic additives or solvents are used, these effectively sinter the compound, but cause precipitation of secondary phases that impede grain-to-grain contacts and the polarization coupling, and result in electrically conductive samples. We found that it is critical to carefully select the sintering additives based on their reactivity, decomposition temperature and products, while ensuring a significant level of wettability and matrix solubility. NaOH/KOH mixture was found to be the best sintering aid, resulting in remanent polarization and strain responses of cold-sintered BFO comparable to those reported for conventionally sintered ceramics.

Ferroelectric thin films are proving their potential for non-volatile memory applications owing to their inherent polarization. The modulation in the conductance of BaTiO3 by doping with Sm3+ ion under dark and illuminated conditions has been studied in this work. Polycrystalline thin films of pristine BaTiO3 (BTO) and Sm-doped BaTiO3 (SBTO) were fabricated on FTO coated glass substrates using the Sol-gel spin coating route. BTO and SBTO thin films exhibited a tetragonal phase and a thickness of 500 nm. The current-voltage (I-V) data of the Al/ SBTO/FTO device show analog bipolar resistive switching under dark and illuminated conditions. The devices have a RON/ROFF ratio of 10 and charge retention up to 103 s. The resistive Switching performance of the Al/ SBTO/FTO device improved under the illumination of UV light (lambda = 395 nm and power of 10 mW/cm2), which makes the device suitable for an Opto-memristor. The long-term potentiation (LTP) and long-term depression(LTD) characteristics of the Al/SBTO/FTO device indicate more linear behaviour than the Al/BTO/FTO device in both dark and illuminated conditions. Thus, Al/SBTO/FTO devices can be useful in non-volatile resistive random-access memory (RRAM).

The nature of lead zirconate, the historical antiferroelectric material, has recently been challenged. In PbZrO3 epitaxial films, thickness reduction engenders competition among antiferroelectric, ferrielectric and ferroelectric phases. All studies so far on PbZrO3 films have utilized commercially-available oxide single crystals with large compressive lattice mismatch, causing the films to undergo strain relaxation. First-principles calculations have predicted that tensile strain can stabilize antiferroelectricity down to the nanometre scale. Here we use tensile strain imposed by artificial substrates of LaLuO3 to stabilize a pure antiferroelectric phase in PbZrO3. Sharp double hysteresis loops of polarization vs electric field show zero remanent polarization, and polar displacement maps reveal the characteristic up-up-down-down antipolar pattern down to 9 nanometre film thicknesses. Moreover, the electron beam can move this antipolar pattern through the nucleation and annihilation of translational boundaries. These results highlight the critical role of coherent epitaxial strain in the phase stability of PbZrO3.

Collective excitations such as magnons and polar phonons provide natural access to the terahertz (THz) regime, but efficient generation and tunability remain elusive. Multiferroic BiFeO3 combines both orders at room temperature, offering a unique platform for narrowband THz emission. Here, we achieve efficient sub-bandgap optical rectification of coupled phonon-polaritons near 2 THz in bare epitaxial thin films. In Pt/BiFeO3 bilayers, we demonstrate that coupling the electromagnon branch with ultrafast strain waves, optically generated in Pt layers with various thicknesses, can produce tunable and narrowband emission between 0.4-0.8 THz. These results uncover the intertwined role of phonons, magnons, and magneto-acoustic dynamics in antiferromagnetic multiferroics, and establish these hybrid platforms as versatile engineered narrowband THz sources.

This paper investigates the synthesis and properties of neodymium-doped bismuth ferrite (BiFeO3) nanoparticles, highlighting their enhanced functionality for advanced applications. The nanoparticles were successfully synthesized with a sol-gel method, where neodymium (Nd) was substituted into the A-site in concentrations ranging from 6% to 10%. A comprehensive analysis of the structural, morphological, and dielectric properties was conducted. X-ray diffraction (XRD) and Rietveld refinement confirmed that all samples maintained a rhombohedral crystal structure with the R3c space group. The incorporation of Nd cations was found to significantly alter the intrinsic distortion of the FeO6 octahedron within the lattice, which is identified as a primary mechanism for property enhancement. Morphological studies showed that the nanoparticles were uniform, with grain sizes between 160 nm and 195 nm. Furthermore, XPS confirmed the presence of Fe2+ ions, which are directly linked to the improved ferroelectric performance. An extensive study of the dielectric properties revealed a change in the electrical conduction mechanism with temperature and notable relaxor behavior. A reduction in the N & eacute;el temperature and increased thermal sensitivity were also detected. These remarkable findings demonstrate that Nd substitution is highly effective in tailoring the properties of bismuth ferrite, making these modified nanoparticles excellent candidates for next-generation devices.

Insulating antiferromagnets are anticipated as the main protagonists of ultrafast spintronics, with their intrinsic terahertz dynamics and their ability to transport spin information over long distances. However, ultrafast transfer of spin angular momentum to an antiferromagnetic insulator remains to be demonstrated. Here, studying the picosecond and subpicosecond dynamics of ferromagnetic metal/antiferromagnetic insulator bilayers, we evidence the generation of coherent terahertz excitations in the antiferromagnet combined with a modulation of the demagnetization behavior in the ferromagnet. We thus demonstrate that magnetic information can indeed be propagated into antiferromagnetic spin waves at picosecond timescales, thereby opening an avenue toward ultrafast manipulation of magnetic information.

BiFeO3/LaFeO3 (BFO/LFO) epitaxial superlattices (SLs) with different bilayer thicknesses were grown via pulsed laser deposition on a (001)-SrTiO3 substrate buffered with a SrRuO3 bottom electrode. Room-temperature X-ray diffraction demonstrated strong structural changes in tuning the bilayer thickness while keeping the total thickness constant. Superlattices with thin periods were characterized by an antiferroelectric Pnma-like phase, while thick bilayers of the SLs were more likely to be described by a mixed state, including a rhombohedral ferroelectric bulk-like phase. Raman scattering analysis further confirmed the structural behaviour deduced by X-ray diffraction. Strain relaxation and symmetry changes were moreover accompanied by modifications in the dielectric properties correlated with the deduced (anti)ferroic structural phases.

Differential calculus is the cornerstone of many disciplines, spanning the breadth of modern mathematics, physics, computer science, and engineering. Its applications are fundamental to theoretical progress and practical solutions. However, the current state of digital differential technology often requires complex implementations, which struggle to meet the extensive demands of the ubiquitous edge computing in the intelligence age. To face these challenges, we propose an in-memory differential computation that capitalizes on the dynamic behavior of ferroelectric domain reversal to efficiently extract information differences. This strategy produces differential information directly within the memory itself, which considerably reduces the volume of data transmission and operational energy consumption. We successfully illustrate the effectiveness of this technique in a variety of tasks, including derivative function solving, the moving object extraction and image discrepancy identification, using an in-memory differentiator constructed with a crossbar array of 1600-unit ferroelectric polymer capacitors. Our research offers an efficient hardware analogue differential computing, which is crucial for accelerating mathematical processing and real-time visual feedback systems.

The substitution of bismuth by samarium in BiFeO3 is known to induce a structural phase transition from the polar phase to a non-polar phase, with a possible antiferroelectric intermediate structure. In this paper, we investigate the impact of this phase change on the optical properties. The optical band gap was measured by diffuse reflectance as a function of temperature for several samarium concentrations across the structural phase transition. We found that the optical band gap for each of the pure phases varies linearly with temperature and that the phase transitions are revealed by smooth transitions between those linear regimes. This allows us to quantify the contribution of the structural change in the optical absorption. We find that a difference in optical band gap of about 130meV can be attributed to the phase change. We anticipate that the same change could be obtained by applying an electric field in an antiferroelectric composition.