Two-dimensional (2D) van der Waals (vdW) ferromagnets are promising for the development of novel physical paradigms and next-generation spintronics. However, their practical applications are limited by a low Curie temperature (TC) and the strong thickness dependence of TC, which decreases significantly toward the 2D limit. 2D Fe-M-Te (M = Ge, Ga) compounds have emerged as key platforms, exhibiting intrinsic ferromagnetism below but near room temperature in few-layer Fe-Ge-Te and above room temperature in few-layer Fe-Ga-Te. This review discusses their recent advances and challenges, especially about the first well above-room-temperature intrinsic 2D vdW ferromagnet Fe3GaTe2 which makes room-temperature practical 2D spintronic and quantum devices possible. The preparation and properties are first summarized, followed by magnetism regulation strategies (e.g., doping, pressure, electrical control, and interfacial engineering) and vdW spintronics (e.g., topological spin textures, vertical spin valves, and spin/orbital torque devices). Finally, some fundamental and technological challenges are highlighted, providing insights into room-temperature spintronics based on vdW ferromagnets.
Chirality engineering offers a plethora of fascinating properties and ushers in compelling applications in spintronics, chiroptics, superconductivity, catalysis, etc. Atomically thin two-dimensional (2D) layered materials have extraordinarily inherent optical, electronic, and quantum properties, accompanied by highly tunable van der Waals heterostructures, making them ideal platforms to engineer chirality. Although the deliberate incorporation of chiral molecules into local coordination environments has imparted remarkably tailored chiroptical and spintronic responses in synthetic systems, such as organic frameworks and hybrid organic-inorganic perovskites, translating such chiral control into the well-explored 2D layered materials (e.g., graphene and transition metal dichalcogenides) faces substantial hurdles, including precise nanostructure fabrication, molecular assembly, subtle chiral coupling, and reliable electronic and optical characterization. This review systematically outlines up-to-date feasible strategies for chiral engineering in 2D layered materials to leverage their functional landscape and unlock the emergent chiral properties. It begins with intrinsic and extrinsic engineering approaches, highlighting the underlying design principles and the resulting novel physical and chemical behaviors. We further discuss potential extensions of these chirality-engineering approaches and explore future promising opportunities that harness rationally tailored chiral functionalities in 2D systems for next-generation optoelectronics, spintronics, and quantum information science.
Altermagnetic multiferroics offer a promising route to low-power spintronics by enabling spin splitting without net magnetization, extending beyond conventional spin-orbit coupling. However, achieving deterministic electric control has remained elusive. Here, a six-state platform for high-dimensional magnetoelectric coupling in altermagnets is established by exploiting the nondegenerate transition paths of sliding ferroelectrics as a symmetry-engineering knob, thereby transcending the conventional binary (up/down) paradigm of sliding ferroelectricity. First-principles calculations on bilayer manganese phosphorus trisulfide reveal a spin-polarization symmetry-locking mechanism. Polarization switching along the three nondegenerate paths not only reverses the spin splitting but also rotates its spin-splitting texture in 120° increments, yielding six nonvolatile, electrically addressable altermagnetic states. Furthermore, direct correspondence is established between the spin-splitting texture and the nonlinear Hall response, providing unique electrical fingerprints for each state. This work establishes a paradigm for electric field-driven reconstruction of momentum-space spin geometry, providing a versatile platform for controlling quantum phenomena in altermagnetic spintronics.
Two-dimensional magnetic materials with an atomic-thick layered structure have long been a focal point in condensed matter physics owing to the intrinsic long-range magnetic order, the monolayer limit with high tunability and potential in nano-scale spintronics. In this study, we report a novel family of two-dimensional (2D) materials, EuOX (where X = F, Cl, Br, I), displaying 2D half-metallicity with topological properties. Specifically, the spin-up conducting channel demonstrates metallic behavior, while the spin-down channel exhibits an insulating band gap at the Fermi level. The presence of Weyl points and nodal lines coexists in the spin-up conductive channel of EuOX monolayers. These topological properties, alongside the half-metallic behavior, evolve systematically with the strong-correlation Hubbard U. These findings provide crucial insights into the design of 2D topological spintronic devices, offering a promising platform for future spintronic applications in the nano scale.
Chiral organic molecules are emerging as key materials in the field of spintronics, primarily because of the chirality-induced spin selectivity (CISS) effect. This phenomenon has provided valuable insights into how nonmagnetic chiral structures can exhibit significant spin selectivity exclusively as a result of their inherent chirality. Previous studies on CISS in organic molecules have primarily focused on cases where spin polarization arises from the intrinsic chirality of monomers or from achiral monomers influenced by a chiral solvent. However, there has been no experimental evidence demonstrating that an achiral segment within a molecule, even in the presence of a chiral group, can drive the CISS effect. Here, we investigate the experimental observation of the CISS effect in peptide-based helical nanofibers, where spin selectivity can be switched by altering the length of achiral spacers between the rigid chromophore and the chiral terminal residue. Our findings reveal a distinct odd-even effect: molecules with an even number of methylene spacers exhibit one type of spin selectivity, while those with an odd number of methylene spacers display the opposite spin preference. We have utilized magnetic-field-dependent atomic force microscopy (mc-AFM) and Kelvin probe force microscopy (KPFM) techniques to demonstrate a robust relationship between chirality and spin transfer. Additionally, to obtain more insight into the spin-dependent transport process, we fabricated a prototype device of spin-valve configuration. It is important to note that the device results not only validate the occurrence of the CISS effect in these studied materials but also correlate well with the findings from spin-dependent processes observed in both the mc-AFM and KPFM measurements. Furthermore, we have successfully demonstrated an innovative approach by investigating the role of the achiral solvent ratio on the spin-dependent transport properties through helical nanofibers.
An intercalated transition-metal dichalcogenide Co 1 / 3 TaS 2 ${\rm Co}_{1/3}{\rm TaS}_{2}$ hosts a triple-Q (3Q) noncoplanar antiferromagnetic state that co-exists with Z 3 $Z_{3}$ electronic nematicity, indicating broken threefold rotational symmetry. This nematicity exhibits versatile field- and strain-tunability, making it promising for spintronics applications. However, its microscopic connection to magnetism has remained unclear. Here, we report rotational hysteresis observed in both magnetoresistance and magnetic torque, revealing strongly pinned in-plane weak ferromagnetic moments in the triple-Q phase and the magnetism-driven nature of the co-existing nematicity. In particular, when fields are rotated within a narrow angular range to restrict magnetization reversal, we observe additional hysteresis loops. This hysteresis can be well explained by domain repopulation, further supported by our theoretical simulations based on the spin Hamiltonian of Co 1 / 3 TaS 2 ${\rm Co}_{1/3}{\rm TaS}_{2}$ . These results demonstrate that the weak in-plane ferromagnetic moment offers an additional handle on the spin-driven electronic nematicity, providing a microscopic picture of the field-tunable electronic responses in the 3Q state of Co 1 / 3 TaS 2 ${\rm Co}_{1/3}{\rm TaS}_{2}$ .
Magnetic materials exhibiting bistability under ambient conditions are highly attractive for applications in data-storage, memory devices, sensors, and stimuli-responsive technologies. Cyanide-bridged octacyanometallates provide a uniquely versatile platform for constructing molecular architectures with tunable electronic and magnetic properties. Here, we present two structurally related cyanide-bridged 2D hexagonal [W─Co] networks that combine structural adaptability with multifunctional switching. Complex 1 {[W(CN)8]2[Co(V-im)4]3}n, undergoes a rare single-crystal-to-single-crystal (SC-SC) transformation to yield complex 2 {[W(CN)8]2[Co(V-im)4]2[Co(V-im)2(DMF)2].4H2O}n, enabling a direct structure-property correlation within the same material system. Complex 1 displays a reversible, single-step, thermally induced metal-to-metal electron transfer (MMET), while complex 2 exhibits a two-step MMET process operating near ambient temperature. Both complexes further demonstrate light-induced bistability: near-infrared irradiation (808, 900 nm) drives conversion of the diamagnetic {WIV LS-CN-CoIII LS} ground state to a metastable paramagnetic {WV LS-CN-CoII HS} state, which is reversibly switched OFF by visible-light irradiation (405, 635 nm). The bistability is unambiguously established by combining variable-temperature magnetic susceptibility, photomagnetic measurements, and synchrotron x-ray absorption spectroscopy, which directly probes the local electronic reorganization at W and Co centers. This work demonstrates how molecular engineering of cyanide-bridged 2D frameworks can deliver robust, multi-stimuli-responsive bistable materials that operate close to room temperature, offering a promising platform for molecular spintronics and optoelectronic devices.
Geometrical frustration on triangular lattice is expected to exhibit diverse quantum spin and electronic states endowed with emergent electromagnetic phenomena. The all-in-all-out (AIAO)-type antiferromagnetic spin structure is one such example, possessing the scalar spin chirality that generates giant emergent magnetic field with vanishingly small magnetization. Here, we report on the large spontaneous magneto-optical Kerr effect (MOKE) caused by the AIAO/AOAI state in quasi-two-dimensional triangular-lattice compound CoNb3S6. Over the entire measured energy region from 55 to 2000 meV, the MOKE is found to be dominated only by the spin chirality. Essential role of momentum-space Berry curvature for both MOKE and dc Hall effect is demonstrated by the spectral analysis of optical Hall conductivity derived from MOKE. The figure of merit of observed topological MOKE, light-polarization rotation angle divided by magnetization, largely exceeds other magnets including time-reversal-symmetry broken antiferromagnet Mn3Sn. Our findings demonstrate the strong light-spin coupling through the spin chirality, paving the way for antiferromagnetic spintronics and future optospintronic devices.
Altermagnetism, an emergent magnetic phase featuring compensated collinear magnetic moments and momentum-dependent spin splittings, has recently garnered widespread interest. A critical issue concerns whether the unconventional spin structures can generate spontaneous electric polarization in altermagnets, thereby achieving type-II multiferroicity. Here, with the combination of symmetry analysis and metal-ligand model, we explicitly demonstrate the generation of electric polarization by altermagnetic Néel order. We further uncover the locking behaviors between Néel order and electric polarization, which are classified into eight distinct categories for two-dimensional altermagnets governed by layer group symmetries. Then we take monolayer MgFe2N2 as a prototypical example of altermagnetic type-II multiferroics by first-principles calculations. We also propose to identify the Néel order and accompanying electric polarization in altermagnetic multiferroics by magneto-optical microscopy. Bridging type-II multiferroics and altermagnets, our work could pave the way for altermagnetic multifunctional spintronics.
RuO₂ was initially proposed as an altermagnet, but this view is now contested and no longer widely accepted. In this work, we have designed and investigated a series of rutile (RuO2)m/(TiO2)n superlattices stacked in the (001) direction using density functional theory (DFT) calculations. Our calculations reveal that altermagnetism emerges in the two-dimensional (2D) RuO2 layers when isolated by sufficiently thick TiO2 spacers. Spin-real-space symmetry in even-numbered Ru layers drives this altermagnetism. The magnetic moments of Ru ions are relatively large at the interfacial layers (up to 0.8 μB), primarily induced by interface effects, but decline to ~0.1 μB in the central regions of the 2D RuO2 slab. This pronounced layer-dependent moment reduction and electronic structure variation are attributed to quantum confinement effects, demonstrating a significant difference compared to the bulk RuO2. Furthermore, by accounting for electronic correlation effects (DFT + U), we observe not only an enhancement of the Ru magnetic moments to ~1.4 μB, but also thickness-driven phase transitions: insulating states dominate in thinner 2D RuO2 (m ≤ 6), while metallic behavior emerges in thicker cases (m > 8). Thus, the (RuO2)m/(TiO2)n superlattices are tunable platforms for engineering 2D altermagnetism, providing new insights into altermagnetic spintronics.
This study reports on the structural, optical, and magnetic properties of Cr-doped ZnO nanorods (NRs) fabricated via a one-step electrochemical deposition process. The impact of Cr3⁺ doping was systematically investigated across concentrations of 0.00, 0.1, 0.5, 0.7, and 0.9 mM, with the resulting samples labelled S0, S1, S2, S3, and S4, respectively. The XRD confirmed the successful substitution of Cr3⁺ into the wurtzite ZnO lattice, but with a few amounts of the ZnCr₂O₄ secondary phase obtained at 2θ = 43.5° for S3 and S4. The SEM micrographs show a significant morphological evolution from high-aspect-ratio nanorods to stubby, thickened structures. In general, the crystallite size and the ratio of diameter/length increase against Cr doping up to S3 and then decrease. The Cr-doped NRs (S1-S4) show enhanced absorption in the visible region (400-600 nm) compared to undoped S0. Additionally, the increase in the Cr leads to a decrease in the optical band gap from 3.42 eV for S0 to 3.23 eV for S4, as determined by Tauc's plot. All NRs exhibit ferromagnetic and diamagnetic behavior at 300 K, whereas the behavior changes to ferromagnetic and paramagnetic with decreasing temperature to 10 K. In addition, the M-H curve develops a little bit of curvature between 0.00 and 3000 Oe to be likely similar to the well-known hysteresis loop of ferromagnetism. To isolate the intrinsic ferromagnetic signal, we subtracted the linear diamagnetic or paramagnetic background from the raw M-H data. The extracted ferromagnetic parameters of (Ms), coercive field (Hc), squareness (Sq), and anisotropy (γ) are obtained, and it is found that they are dependent on the chosen Cr concentration and temperature. Although most of them are affected by Cr doping, the values of Ms and γ at 10 K are higher than those of 300 K, whereas the vice is true for the Hc and Sq. The field cooling (FC) and zero-field cooling (ZFC) curves of S0 and S1 splitting across the temperature range (10-300 K). In contrast, introducing Cr drastically changes this picture since FC and ZFC curves completely overlap with each other. The Curie temperatures are between 299.95 and 299.99 K for the NRs (S0-S4). These findings establish electrochemical deposition as a viable route for fabricating Cr:ZnO NRs with narrow band gaps; paramagnetic and RTFM behaviors are tuneable multifunctional properties in visible-light optoelectronics, medical treatments, and spintronics.
The efficiency of oxygen reduction and evolution reactions is fundamentally constrained by macroscopic mass transport bottlenecks at the triple-phase interface and the quantum-mechanical restriction of spin-forbidden transitions. This review presents a multilevel framework to overcome these barriers. At the macroscopic solid-liquid-gas boundary, bio-inspired and asymmetric wettability architectures enable the decoupling of gas and ion transport channels, thereby alleviating diffusion-limited current scaling. At the atomic level, defect engineering, size control, heteroatom doping and synergistic heterointerface construction regulate local electronic structure and oxygen intermediate adsorption. Beyond intrinsic material design, external physical fields act as dynamic levers, ranging from magnetohydrodynamic enhancement of bubble detachment to magnetic exchange interactions for spin alignment. We further highlight chiral spintronics, where the chiral-induced spin selectivity effect provides an intrinsic field-free route for spin filtering. By promoting parallel spin alignment of radical intermediates, intrinsic chirality facilitates triplet oxygen formation. Finally, we integrate these multilevel strategies to outline a path toward next-generation oxygen electrocatalysts, while identifying critical challenges in stability, spin-sensitive operando characterization, standardized evaluation, and practical scalability.
Single-walled carbon nanotubes (SWCNTs) act as one-dimensional (1D) nanoreactors capable of stabilizing reactive species and unique low-dimensional phases. Here, we report the synthesis of an unprecedented 1D Sc3Cl8 phase formed via the confinement-induced structural reconstruction of bulk ScCl3 within SWCNTs. The atomic structure of the Sc3Cl8@SWCNT heterostructure is determined by combining aberration-corrected electron microscopy (HRTEM/STEM) with machine-learning force field (MLFF) global structure searches. This reconstruction yields a metal-rich phase that exhibits two anomalous properties. First, unlike typical halide fillers that induce p-type doping, the Sc3Cl8 chain acts as a potent electron donor, driving a strong n-type charge transfer to the nanotube host (a phenomenon we term "redox inversion"). Second, spin-polarized density functional theory (DFT) predicts that the confined chain possesses a ferromagnetic ground state, emerging from a diamagnetic bulk precursor. These results identify Sc3Cl8@SWCNTs as a model heterostructure where confinement simultaneously inverts doping polarity and unlocks magnetic potential, offering a new platform for carbon-based spintronics.
Chalcogenide ferroelectric Rashba semiconductors (FERSCs) offer a promising route to ultralow-power spin-orbit devices, yet their integration into microelectronics has been hindered by the lack of high-quality films grown using industry-compatible methods. Here, we demonstrate CMOS-compatible synthesis of rhombohedral α-GeTe(111) thin films on 200/300 mm Si wafers using an industrial deposition process based on van der Waals epitaxy, applied to this material class for the first time. Scanning Transmission Electron microscopy and advanced simulations of anomalous X-ray diffraction measurements at synchrotron reveal that films are intrinsically self-poled, exhibiting a robust upward out-of-plane ferroelectric polarization. The growth strategy is universal, enabling high-quality α-GeTe(111) on metals and insulators without compromising structural or ferroelectric performance. Piezoresponse force microscopy confirms reversible 180° ferroelectric switching with performance comparable to molecular-beam-epitaxy benchmarks. This substrate-independent growth strategy represents a decisive step toward the future large-scale integration of FERSCs into functional spin-orbit architectures, with the hope of bridging the gap between Rashba's fundamental physics and microelectronic implementation.
The exchange bias effect serves as one of the core working mechanisms in spintronic devices. Investigating the angular dependence of exchange bias (ADEB) is of significant importance for understanding the microscopic mechanism of the exchange bias effect. Currently, the characteristics of magnetization reversal in in-plane orthogonal anisotropy systems remain unclear, while hard magnetic (HM)/soft magnetic (SM) systems exhibit distinct advantages over conventional antiferromagnetic/ferromagnetic systems. In this context, it is of considerable value to conduct an in-depth exploration of the ADEB phenomenon in in-plane orthogonal anisotropy systems using HM/SM systems as the research subject. In this work, based on micromagnetic simulations, we systematically investigate the exchange bias effect and magnetization reversal behavior in the FeCo layer ofL10FePt (HM)/FeCo (SM) bilayer thin-film structure with in-plane orthogonal anisotropy. The results demonstrate that the magnetization reversal mechanism in the FeCo layer can be effectively modulated by varying the FeCo layer thickness and the direction of the applied magnetic field. The angular dependence of the exchange bias field, coercivity, and magnetization reversal all exhibit rich and diverse behaviors with changes in the FeCo layer thickness. These findings provide additional insights for the application and modulation of the exchange bias effect in spintronic devices.
Self-assembled monolayers of polyalanine α-helices exhibit distinct structural phases with implications for chiral-induced spin selectivity. We combine scanning tunneling microscopy and theoretical modeling to reveal how chiral composition governs supramolecular organization. Enantiopure systems form hexagonal lattices, while racemic mixtures organize into rectangular phases with stripe-like features. Our interaction potentials derived from density-functional based tight binding calculations show that opposite-handed helix pairs exhibit stronger binding and closer packing, explaining the denser racemic structures. Crucially, we demonstrate that the observed STM contrast arises from antiparallel alignment of opposite-handed helices rather than physical height variations. These findings establish fundamental structure-property relationships for designing peptide-based spintronic materials.
Tungsten ditelluride is a layered semimetal with higher-order topological insulator properties and robust one-dimensional (1D) states along certain crystallographic axes, making it promising for future spintronic applications. While bulk and exfoliated materials have been extensively studied, WTe2 nanoribbons and nanowires offer advantages for probing edge-state physics due to their enhanced surface-to-volume ratio and confined geometry. However, existing growth approaches for producing WTe2 nanostructures struggle to yield materials of sufficient quality. In this work, we investigate the growth and charge transport characteristics of WTe2 nanoribbons (NRs) synthesized through the tellurization of WO3 nanoribbons, comparing how different precursor compositions, WO3 with and without a NaCl:Te additive, alter the resulting material properties. The tellurization of the ribbons obtained using a NaCl:Te additive allows the production of highly crystalline WTe2. Charge transport measurements for individual WTe2 nanoribbon four-terminal devices indicate that surface capping is essential to prevent rapid oxidation. This study establishes a pathway for the fabrication of freestanding WTe2 nanoribbons of different geometrical parameters via the tellurization process.
Recent years have witnessed the emergence of spin supersolids in frustrated quantum magnets, establishing a material-based platform for supersolidity beyond its original context in solid helium. A spin supersolid is characterized by the coexistence of longitudinal spin order that breaks lattice translational symmetry and transverse spin order associated with the spontaneous breaking of the spin U(1) symmetry. Extensive experimental investigations, together with advanced numerical studies, have now revealed a coherent and internally consistent picture of these phases, substantially deepening our understanding of supersolidity in quantum magnetic materials. Beyond their fundamental interest as exotic quantum states, potential applications in highly efficient demagnetization cooling have been supported by a giant magnetocaloric effect observed in candidate materials. Moreover, the possible dissipationless spin supercurrents could open promising perspectives for spin transport and spintronic applications. This review summarizes recent progress on emergent spin supersolids in frustrated triangular-lattice quantum antiferromagnets, surveys experimental evidence from thermodynamic and spectroscopic measurements, and compares these results with theoretical studies of minimal models addressing global phase diagrams, ground state properties, and collective excitations. In addition, this review discusses characteristic spin-transport phenomena and outlines future directions for exploring spin supersolids as functional quantum materials.
Spin filtering and its back-action spin-transfer torque (STT) are key ingredients of the latest spintronic devices based on magnetic tunnel junctions (MTJs). Resonant tunneling (RT), implemented by design or occurring as parasitic effects, is known to crucially affect macroscopic device performance, but direct experimental access to its individual microscopic processes has remained difficult. Here, we apply the RT scheme from MTJs to spin-polarized scanning tunneling microscopy (SP-STM) for ultimate miniaturization obtained by addressing distinct sites on individual nanomagnets. Combined with energy selectivity, our experimental model setup enables us to study the spin filtering capabilities of RT through an individual spin-split vacuum resonance state and of the corresponding STT exerted on the nanomagnet. We find that the sign and magnitude of the STT follow the effective spin-polarization of the resonance state, which, as we show, can be tailored on demand either by adjusting the applied bias or the current injection point on the nanostructure. We anticipate that our atomic-scale RT-MTJ approach and the discovery of a versatile tunable spin filter at the smallest scale will prove invaluable for studying and designing next-generation MTJs, potentially based on recently discovered 2D van-der-Waals magnets or altermagnets.
Two-dimensional chiral covalent organic frameworks (2D-CCOFs) stand out as excellent candidates for chiral spintronic devices owing to their tailorable semiconducting structures and intrinsic chiral sites. However, two critical challenges currently hinder their development: first, the difficulty in synthesizing highly crystalline 2D-CCOF films and, second, the lack of reliable methods to construct stable 2D-CCOF-based spintronic devices. Herein, we successfully synthesized a 2D-CCOF film featuring a high crystallinity and excellent conductivity. In situ magnetic conductive-probe AFM (in situ mCP-AFM) characterization confirms that this 2D-CCOF exhibits excellent chiral-induced spin selectivity (CISS), with a spin polarization over 90% at room temperature. Using graphene as a blocking layer, we have successfully constructed stable half-spin valve devices based on the 2D-CCOF, which exhibit distinct chirality-dependent magnetoresistance. Graphene plays a key role in mitigating the detrimental effect of electrode deposition on the CCOF films. The excellent spin selectivity of 2D-CCOF opens up unprecedented opportunities for efficient control of electron spin and enables solid-state chiral spintronic devices.