Altermagnets combine magnetic compensation with spin-momentum-locked splitting in the absence of spin-orbit coupling, yet existing descriptions, formulated primarily in terms of spin symmetry and lattice geometry, provide limited insight into the electric-structure perspective of its angular harmonic form. Here, we identify a wavefunction-level framework for altermagnetism in two-dimensional square lattices. Using symmetry-adapted polynomial wavefunctions, we show that the harmonic structure of momentum-space spin splitting is inherited from the geometry of the electronic wavefunctions which can be selected by crystal fields. Identical orbital sectors preserve conventional antiferromagnetic degeneracy, whereas intertwined linear and quadratic wavefunctions generate d-wave and g-wave altermagnetic anisotropies, respectively. Tight-binding analysis connects this hierarchy to inequivalent same-spin hopping channels. First-principles calculations on the g-wave mcm-type reticular material platforms confirm high-symmetry-linear degeneracy together with finite generic-k splitting. Our results establish a hierarchy linking wavefunction geometry, orbital realization, microscopic hopping anisotropy, and altermagnetic electronic structure.

Rational design of two-dimensional (2D) room-temperature magnetic metal-organic frameworks (MOFs) requires a fundamental understanding of how organic ligand properties dictate magnetic ordering temperatures (TC). Here, we demonstrate that the degree of pi-orbital conjugation of the ligand is a decisive factor controlling magnetic coupling strength and TC in 2D MOFs. Through first-principles designing, we investigate a family of honeycomb-kagome Mn2L3 monolayers (L = C6N4H6, C6O4H2, C6S4H2). All three frameworks are ferrimagnetic Dirac half-metals with TC values spanning 304 to 653 K. The high-temperature magnetism originates from strong d-p exchange between Mn4+ ions and partially occupied molecular orbitals (POMOs) on the ligands. Crucially, the conjugation degree of these POMOs, quantified by the nucleus-independent chemical shift (NICS), dictates the strength of d-p orbital hybridization and thus magnetic coupling. We thereby establish the NICS value of the free ligand as an effective electronic descriptor for predicting TC, offering a promising ligand-centered strategy for engineering room-temperature magnetism in 2D MOFs.

Two-dimensional (2D) molecular ferromagnets with robust room-temperature magnetism remain elusive due to weak intermolecular interactions and structural instability. Herein, we present an interlayer-confined molecular assembly strategy to construct a family of 2D room-temperature molecular ferromagnets within metallic van der Waals (vdW) hosts. Using cobaltocene-intercalated TaS2 as a prototype, we achieve precise molecular orientation control and enhanced spin alignment through vdW confinement. Strong organic-inorganic interfacial coupling mediates itinerant-electron-driven ferromagnetic exchange, resulting in long-range ferromagnetic order above 300 K and a notable negative magnetoresistance (-5.7% at 300 K). The strategy is applicable to multiple metallic transition-metal dichalcogenides, establishing a general approach to molecularly engineered 2D spintronic materials. This work highlights the power of confined molecular assembly in discovering 2D ferromagnets and functionalizing magnetic small molecules.

Altermagnets are symmetry-defined magnetic phases that combine momentum-dependent spin splitting with zero net magnetization, offering promising opportunities for spintronics. However, their realization is strongly constrained by rigorous symmetry requirements. Exploiting the shared antiparallel magnetic order and vanishing net magnetization between antiferromagnets and altermagnets, we propose a general chemically driven strategy based on asymmetric ligand modification to transform pristine two-dimensional antiferromagnetic metal-organic frameworks into altermagnetic candidates. Using chromium phthalocyanine (CrPc) as a proof-of-concept model, we show that asymmetric modification lowers the local site symmetry at magnetic Cr centers and generates momentum-dependent spin splitting and anisotropic spin densities, as revealed by first-principles calculations. Oxygen-modified CrPc derivatives further illustrate the chemical tunability of this symmetry-control principle. Our work expands the design space of organic altermagnetic candidates and establishes a chemically grounded route for engineering symmetry-governed magnetic functionality in reticular materials.

Inorganic electrides are conventionally defined by a positive formal oxidation-state sum, necessitating frameworks with cavities or channels to accommodate charge-balancing anionic electrons. Here, we identify a distinct class of "hidden electrides": alkali auride bimetallenes exhibiting a zero formal oxidation-state sum, yet hosting interstitial anionic electrons (IAE) clearly evidenced by electron localization function and charge density analyses. By manipulating the surface arrangement of alkali metals, we demonstrate a general strategy to program the topology of these anionic-electron lattices, realizing a family of two-dimensional bimetallenes with tailored electronic distributions, including Janus-type monolayer configurations. First-principles calculations reveal that these hidden electrides possess exotic electronic structures characterized by Dirac-like crossings, flat bands, and van Hove singularities dominated by IAE. Comprehensive stability screening identifies Li-Au bimetallenes as particularly robust systems that combine low formation energies with ultralow work functions (down to 2.27 eV). Furthermore, in heterostructures with MoS2, these bimetallenes form ohmic contacts and achieve electron injection levels up to 3.98 & times; 1014 cm- 2, establishing them as promising candidates for low-barrier electron injection layers in next-generation nanodevices.

The magnetoelectric coupling in compensated magnets enables stray-field-free manipulation of spin-splitting, holding great promise for spintronics, but inherently hindered by the symmetry mismatch between spatial-inversion-broken ferroelectricity and time-reversal-broken spin states. Here, based on a symmetry-decoupled analysis of magnetoelectric coupling in compensated magnets, we establish a geometry-driven spin-ferroelectric coupling mechanism in bilayer breathing kagome lattices. Within this geometric framework interlocking the out-of-plane electric polarization with cooperative intralayer structural distortions, we demonstrate that polarization switching drives a deterministic reversal of the global spin splitting. First-principles calculations on a prototype bilayer Nb3Cl8 successfully validate this mechanism, demonstrating the switching of spin-splitting states through an energetically feasible, asynchronous layer-by-layer transition pathway. Our proposed coupling originates from lattice geometry and structural symmetry, establishing a unique route toward switchable spin splitting in compensated ferrimagnets.

Fully compensated ferrimagnets (fFiMs), which combine vanishing macroscopic magnetization with spin-split electronic states, are attractive for stray-field-free spintronics. However, achieving exact moment cancellation typically requires fine control over inequivalent magnetic sublattices, making the rational design of fFiMs a fundamental challenge. Here, we propose a general design strategy for two-dimensional (2D) fFiMs by integrating redox-active noninnocent ligands (NILs) into metal-organic frameworks (MOFs). First-principles calculations demonstrate that fractional metal-to-ligand charge transfer converts NILs from closed-shell linkers into a spin-bearing ligand sublattice that aligns antiparallel to the metal centers, enabling stoichiometric moment compensation. We validated this concept in a family of trigonal 2D chromium MOFs. While the prototype Cr(BTT)2 confirms fully compensated ferrimagnetism, it exhibits intrinsic thermal instability. The modular nature of the NIL strategy allows for chemical refinement, and ligand fluorination (Cr(F-BTT)2) or heavy-chalcogen substitution (Cr(BSeT)2) stabilizes the 2D lattice without disrupting the fFiM ground state. The chemically optimized Cr(F-BTT)2 retains fully compensated ferrimagnetism and exhibits a near-Fermi quasi-Dirac-like band feature with an estimated magnetic transition temperature of 132 K. Extended studies of nitrogen- and phosphorus-based ligands further support the generality and boundary of this approach. These findings establish NIL-directed charge transfer as a chemically programmable handle for engineering 2D-compensated magnets.

As a type of high-temperature piezoelectric material, Aurivillius compounds exhibit superior thermal stability and resistivity, yet display a deficiency in piezoelectricity. Currently, despite the successful construction of diverse Aurivillius solid solutions with excellent electro-mechanical properties via composition engineering, this chemical modification necessitates a significant number of trial-and-error experiments, thereby complicating the composition. Herein, based on the typical ferroelectric theory and phase characteristics of Aurivillius compounds, we propose new insight into the piezoelectricity optimization mechanism from the view of relaxation. The introduction of random fields can effectively soften the lattice structure and activate the polarization fluctuation, thereby improving ionic fluctuation, domain dynamics and then piezoelectricity. This finding is believed to provide a systematic framework for optimizing piezoelectric performances, innovating existing piezoelectricity regulation methods and advancing the development of Aurivillius compounds.

Altermagnetism, characterized by momentum-dependent spin polarization in collinear antiparallel spins with vanishing net magnetization, represents a distinct magnetic phase beyond conventional ferromagnetic and antiferromagnetic classifications. This phenomenon arises from unique spin group symmetries that decouple spin and spatial degrees of freedom, enabling nonrelativistic spin-split electronic bands. Integrating this phenomenon with multiferroicity in two-dimensional (2D) materials offers unprecedented opportunities for quantum state manipulation. However, a unified theoretical framework for such multifunctional materials remains underdeveloped. Here, we establish a symmetry-driven framework identifying four point group species (14̅222mF2m2m12, 24̅122mF2m2m12, 24̅F22, and 222212F22) that can simultaneously host altermagnetism, ferroelasticity, and out-of-plane ferroelectricity, termed altriferroicity. First-principles calculations further validate this framework in Fe2WS2Se2 and half-fluorinated Cr-based metal-organic frameworks, revealing robust spin-lattice-charge coupling. Our work establishes symmetry-guided design as a powerful approach for unlocking emergent quantum phenomena in 2D materials for spintronic and valleytronic applications.

The Lieb lattice is fundamental in condensed matter physics for hosting exotic electronic and topological states. Through high-throughput computational screening of 1470 binary metal-inorganic frameworks (MIFs), we identified 24 stable Lieb lattice structures, including 22 new materials. These comprise 15 nonmagnetic, 2 ferromagnetic (FM) half-metals, and 7 antiferromagnetic semiconductors, with critical temperatures reaching 877 K. Key electronic features include flat bands, Dirac cones, and van Hove singularities. HfCl₂ and WO₂ are FM half-metals with large spin gaps (5.37 eV and 3.57 eV), enabling full spin polarization. Be₂C and ReF₂ exhibit nodal loops and quasi-flat bands, respectively, hosting nontrivial topology confirmed by edge-state analysis. Nine MIFs are zero-dimensional electrides with work functions as low as 2.64 eV. Thirteen structures are ground-state phases, ensuring stability. These Lieb lattices offer promising platforms for high-temperature electronic, spintronic, and topological applications.

Bi0.5Na0.5TiO3-based ceramics are a promising lead-free alternative to lead-based counterparts due to large electro-strain. However, high driving electric fields required to trigger the giant strain hinder practical applications. Constructing 2-2 relaxor/ferroelectric composites is an effective and process-simplified method to decrease the driving field. Herein, flat and dense BNKT-0.01Ta/xBNKT 2-2 composite ceramics are fabricated by the solid state reaction, and the variations of driving field and electro-strain with the addition of BNKT layer are investigated systematically. The optimal performance (i.e., high electro-strain & low driving field) is obtained when x = 10 wt%. Under a low electric field of 40 kV/cm, a relatively high electro-strain (similar to 0.33 %) and a large d(33)* (S-max/E-max=843 pm/V) are obtained. Moreover, the electro-strain of composites shows benign temperature stability within 25-105 degrees C. Our work not only provides a simple and efficient method for fabricating 2-2 relaxor/ferroelectric composites but also gives formulations that enable large electro-strain under low driving fields.

Altermagnetism, an emergent collinear magnetic phase with zero net magnetization and momentum-dependent spin splitting, promises to revolutionize spintronics by leveraging symmetry-driven effects without requiring spin-orbit coupling. Despite its potential, a comprehensive understanding of design principles and spin-splitting mechanisms remains elusive. Here, from a mathematical perspective, we exploit the intrinsic fourfold symmetry and structural versatility of 2D square tessellations to engineer altermagnetic states. By systematically screening the altermagnetic state in all 34 2D square tessellations in the Reticular Chemistry Structure Resource database, we identify the "Lieb" (a regular lattice with 4.4.4.4 tessellation), "fes" (a semiregular net with 4.8.8 tessellation), and "tts" (a semiregular net with 3.3.4.3.4 tessellation) nets as key candidates. A tight-binding Hamiltonian analysis reveals the physical origin of spin splitting across these different tessellated nets. As proof of concept, we demonstrate the pyracylene-based metal-organic framework monolayer t-Cr_{2}[Pyc-O_{8}], with the tts net, as a robust altermagnet exhibiting a symmetry-compliant ground state. Our Letter provides a symmetry-driven design framework that bridges the mathematical architecture of tessellations with computational materials discovery, enabling reasonable control of altermagnetism in 2D materials.

Bi0.5Na0.5TiO3 is regarded a potential alternative to lead-based piezoelectric materials due to its large electrostrain. Generally, the improved electro-strain is considered to arise from a relaxor-ferroelectric transition, and the random fields play a critical role. In this study, to investigate the effect of random electric field or strain field on the strain value, the dopant Sb5+, Ta5+, Zr4+, and Hf4+ are introduced into the Bi-0.5(Na0.8K0.2)(0.5)Ti(1-x)BxO(3) matrix, respectively. The 1 % Ta5+ doped sample has the largest unipolar electro-strain, up to 0.49 %, followed by the 3 % Zr4+ doped sample (similar to 0.448 %). The electro-strain of 1 % Sb5+ and 3 % Hf4+ samples are 0.404% and 0.377 %, respectively. The results show the random electric field or strain field can effectively regulate the relaxor-ferroelectric transition temperature, which enhances strain, but the strain value cannot be determined directly. The strain value is determined by the lattice structure before and after the electric field is applied.

Bilayer altermagnets featuring layer-mediated spin-valley locking hold significant promise in spintronics and valleytronics. In this study, we perform a comprehensive symmetry analysis of bilayer altermagnets and identify seven spin point group candidates with spin-valley-layer coupling, including 22, 222212, 24̅, 142222, 24̅221m, 1322, and 162222. Focusing on the platform of bilayer metal-organic frameworks, we theoretically design materials with S4 symmetry through chemical modification, achieving spin-splitting in the valence band. Furthermore, the spin valleys from different layers exhibit tunable responses to external static gate electric fields, enabling precise control of spin-splitting. Our findings presented a framework that integrates spin, valley, and layer degrees of freedom in bilayer altermagnets, paving the way for nanoscale spintronics and valleytronics applications.

The industry has recently expressed an eager demand for piezoelectric materials capable of sensing pressure, acoustics, and vibrations at high temperatures. For high-temperature piezoelectric materials, it is generally incompatible to achieve a high Curie temperature and large piezoelectricity. Herein, we meticulously dope the scandium into the Bi2.96Ce0.04TiNbO9 ceramic to address this dilemma. The doping of scandium causes the oxygen octahedron to rotate and tilt along the direction of spontaneous polarization, enhancing the intrinsic contribution of piezoelectricity. The increased domain size coupled with the facilitated domain rotation leads to an improved extrinsic contribution. Moreover, the scandium doping can improve the resistivity by refining grains and forming defect dipoles to reduce the concentration of oxygen vacancies. The BCTN-2Sc ceramic exhibits excellent electrical comprehensive properties: large piezoelectricity (19.2 pC/N), high Curie temperature (915 °C), large resistivity (6.4 × 105 Ω·cm @600 °C), and superior thermal stability, which make it a promising candidate for high-temperature sensing applications.

Electrochemiluminescence (ECL) is a light-emitting process in which the stability of electrochemically generated radicals has a crucial impact on the efficiency and durability of excited state generation. Therefore, deciphering a relationship between radical stability and ECL performance is highly appealing. In this work, three sp2 carbon-conjugated covalent organic framework (COF) reticular nanoemitters compositing of same pyrene luminophores but different acrylonitrile linkers are designed with progressive electron affinities, named as CN-COF-1, 2, and 3. By precisely modulating the electron affinity of CN-COFs, a volcano relationship between ECL and radical stability is discovered with 78 folds enhancement in ECL intensity. Density functional theoretical calculations indicate that CN-COF-2 exhibits moderate radical stabilization capacity as well as efficient electron transport between the pyrene cores, facilitating ECL generation. Significantly, the appropriate radical stability of CN-COF-2 not only achieves the self-enhanced cathodic ECL but also promotes durability of the ECL intensity. The rational regulation of radical stability paves the way for developing efficient reticular nanoemitters and decoding the ECL fundamentals.

As for assessing strain performances of Na0.5Bi0.5TiO3-based systems, the driving field level is a critical parameter. Currently, both current density and strain rate evaluation methods have been utilized to characterize the driving field. However, we find that some discrepancies indeed exist between these two evaluation methods, especially for the highly ergodic condition. By means of the typical ferroelectric theory, the initial analysis for discrepant current density and strain rate loops reveals that the relaxor-ferroelectric transition is likely to be a multi-step transition process. Dynamic dielectric loss/permittivity evolution further confirms the speculation and suggests that partial transition steps may be consisted of successive transition events. Ferroelectric and dielectric loops not only provide a fantastic view to unravel the multi-step relaxor-ferroelectric transition process, but also guides to regulate the strain appraisal system.

Piezoelectric ultrasonic energy harvesters (PUEHs) have recently attracted increasing attention. For minimizing the energy losses during energy transfer, it is crucial for core piezoelectric materials to maintain high piezoelectric coefficient ( d 33 ), mechanical quality factor ( Q m ), and piezoelectric voltage coefficient ( g 33 ). Herein, a simple way of hardening strategy improves the piezoelectric properties of KNN-based ceramics, combined with optimizing grain growth. The enhanced d 33 (-340 pC/N), high Q m (-211) and T C (-305 degrees C) are obtained simultaneously in this system, accompanied by superior d 33 x g 33 =8770x10 - 15 m 2 /N. Through variable temperature resonance test, the polarization rotation diversity caused by phase structure difference is found to closely related to the temperature stability of Q m value. A prototype of PUEH device was further designed and fabricated, with adjustable ultrasound -induced output voltage up to 8.2 V. Our work exhibits an effective way to improve performance of PUEHs by optimizing piezoelectric materials, which is helpful for further developing PUEHs.

Half-metallicity, enabling 100% spin polarization, is pivotal for spintronics but remains challenging to achieve in low-dimensional materials. Using first-principles calculations, we theoretically propose an experimentally feasible two-dimensional (2D) metal-organic framework (MOF) magnetic semiconductor, Cr(TCNB)2 (TCNB = 1,2,4,5-tetracyanobenzene). This monolayer can be exfoliated from a Ag(100) substrate due to its low exfoliation energy of 0.14 J/m2. Phonon spectra and ab initio molecular dynamics confirm its dynamical and thermal stability up to 600 K. Cr(TCNB)2 exhibits a ferrimagnetic ground state stabilized by direct p-d magnetic interactions. Notably, carrier doping induces half-metallicity, transforming it into a fully spin-polarized conductor. Monte Carlo simulation predicts that doping elevates the Curie temperature above room temperature. This work introduces a novel 2D MOF magnet with carrier-tunable half-metallicity, offering promising potential for flexible and nanoscale spintronic devices.