Licong Peng

Order‐to‐disorder transitions in skyrmion lattices have been explored under spatially uniform stimuli, such as thermal or magnetic fields, which are significant for controlling collective skyrmion behavior for spintronic applications. However, under directional driving by an electric current, how the order of a skyrmion lattice evolves beyond melting into a liquid remains unclear. Here we show that a current‐driven skyrmion lattice does not enter a disordered phase, but instead undergoes a solid‐to‐conformal phase transition with periodically modulated local orientation, using in situ Lorentz transmission electron microscopy (L‐TEM). Unsupervised graph learning, combined with complementary structural order parameters, enables direct real‐time tracking of the lattice reordering. Correlation between orientational order and defect evolution reveals that the transition is mediated by transient dislocation proliferation during the development of the ordered state. These results establish a current‐induced order‐to‐order skyrmion transition and uncover conformal ordering as a distinct nonequilibrium structural state in topological particle assemblies.

Skyrmions carry robust topology, yet their geometry is highly tunable and can shape interactions, dynamics and functionality. However, how geometric confinement couples to helicity and reshapes the effective energy landscape in intrinsically anisotropic skyrmions remains unexplored. Here we demonstrate that skyrmion ellipticity and its magnetic‐field evolution are strongly helicity dependent in 500‐nm‐wide FeNiPdP nanostripes with anisotropic Dzyaloshinskii–Moriya interaction. Confinement compresses clockwise (CW)‐helicity skyrmions toward near‐circular profiles, whereas counterclockwise (CCW)‐helicity skyrmions elongate along the nanostripe axis, breaking the reciprocal ellipticity relation expected in unconfined geometries. Increasing the perpendicular field further reveals a monotonic circularization of CW skyrmions but a clear nonmonotonic response for CCW skyrmions. Energy analysis shows that confinement reshapes the field‐dependent energy landscape and shifts the optimal skyrmion geometry, giving rise to this nonlinear response. The nanostripe constraint also introduces a surface‐localized interstitial vortex texture in anisotropic skyrmions that can evolve into a vortex pair, consistent with our micromagnetic simulations. Our results establish helicity‐resolved confinement as a route to engineer anisotropic skyrmion morphology and emergent surface textures, enabling helicity‐programmable shape and interaction control for multistate skyrmion‐based devices.

Three‐dimensional (3D) topological spin textures host rich internal structures in thickness dimensions and enable emergent topological phenomena. However, whether their layer‐resolved textures and internal singularities fundamentally modify intralayer interactions lies beyond rigid‐tube interaction models and remains unexplored. Here we show that, in 3D hybrid skyrmion‐antiskyrmion strings, the layer‐dependent topology gives rise to interactions with a sign change across the film thickness, producing a switch between attraction and repulsion both among different layers within each texture and between neighboring 3D strings. This vertically asymmetric attractive‐repulsive interaction drives a tunable transition between square and triangular string lattices, in agreement with our experiment. Computational simulations identify quadrupolar Bloch points as internal topological junctions whose vertical migration mediates the intralayer competition between repulsive skyrmion segments near the surfaces and attractive antiskyrmion segments in the interior. We further show that the averaged topological charge quantifies the relative thickness fractions of the two competing topological segments and robustly captures the lattice phase boundary over a broad range of magnetic parameters. These findings highlight the importance of the surface‐bulk difference in topological materials and establish vertically asymmetric interactions as an intrinsic mechanism for topological phase control in 3D magnetic systems.

Two‐dimensional (2D) magnets offer substantial potential for high‐density spintronic memory due to their tunable magnetic states, yet a robust, scalable strategy for controlling domain configurations for 2D magnets remains elusive. Here, a selective non‐uniform nucleation strategy via chemical vapor deposition is proposed to achieve controlled, non‐homogeneous growth of room‐temperature ferromagnetic CrTe nanoflakes. This enables bottom‐up control of domain evolution by leveraging the strong correlation between the thickness profile and magnetization reversal. The stepwise magnetization reversal in multi‐thickness nanoflakes endows CrTe with multiple magnetic states. Utilizing such multi‐thickness CrTe nanoflake, a tunable multi‐state magnetoresistance is successfully realized in vertical spin valve devices. The controlled synthesis of multi‐thickness CrTe nanoflakes signifies a breakthrough in domain‐state control in 2D magnet, and establishes a robust material foundation for potential applications in multi‐state storage and spin encryption communication.

Topological skyrmions can be driven by ultralow electric currents, attracting significant interest for nonvolatile magnetic memory and spintronic devices. However, how electrical current reshapes skyrmions and reorganizes their collective order remains much less explored, despite its importance for geometry-controlled emergent phenomena and functionality. Here we show that electric-current pulses drive the deformation of oriented helical stripes, yielding elongated skyrmionic textures and ultimately assembling a skyrmion lattice in the chiral magnet Co₈Zn₁₀Mn₂ at room temperature. We further capture pronounced intermediate distortions, including elongated and comet-like textures with tail-like extensions, indicating highly nonuniform deformation and local texture inhomogeneity during stripe-to-skyrmion conversion. Beyond nucleation, successive pulses drive the deformation, displacement, and reorganization of skyrmion clusters, yielding a reordered skyrmion assembly. Micromagnetic simulations reproduce the intermediate morphologies and deformation pathways. Our results establish deformation-assisted dynamics as a real-space route by which pulsed currents generate and reorganize skyrmions, linking pinning-mediated deformation to the emergence and evolution of skyrmion order.

Harnessing the spin degrees of freedom offers unprecedented opportunities to engineer electronic band structures and transport behaviors, laying the foundation for spintronic devices. Particularly, the magneto‐Seebeck effect provides direct insight into the interplay among spin order, electron and heat transport. Here, we observe an unconventional giant magneto‐Seebeck effect in the van der Waals (vdW) antiferromagnet (Fe,Co) ₃ GaTe ₂ , reaching −74% at 2 K. First‐principles calculations reveal that the antiferromagnet‐to‐ferromagnet transitions in (Fe,Co) ₃ GaTe ₂ trigger pronounced band re‐construction, significantly modulating the density of states near the Fermi level. We further perform magneto‐electric transport experiments and observe positive magneto‐resistance in (Fe,Co) ₃ GaTe ₂ , a result that validates our theoretical predictions. This work reveals a giant magneto‐Seebeck effect in a vdW antiferromagnet and uncovers the critical role of spin‐state‐dependent electronic band modulation in vdW magnets, providing a novel strategy for designing high‐performance thermoelectric materials via spin state engineering.

Layered magnetic systems with interlayer antiferromagnetic coupling are emerging as a promising platform for energy-efficient spintronic technologies, particularly in the form of van der Waals (vdW) magnets. The direct observation and manipulation of topological spin textures in perpendicularly magnetized 2D antiferromagnets, however, remain highly challenging due to their compensated magnetic states and rigid interlayer exchange, thereby hindering direct insight into spin ordering and functional exploration. Here, using spin-polarized low-energy electron microscopy, we directly visualize antiferromagnetic domains and emergent topological textures in the vdW antiferromagnet (Fe_1-xCo_x)₃GaTe₂. We uncover tuneable stripe-like domain configurations that can be reconfigured into antiferromagnetic skyrmions under external stimuli, despite the absence of remanent magnetization. These results provide direct insight into spin ordering in a perpendicularly magnetized layered two-dimensional antiferromagnet and open new avenues for next-generation antiferromagnetic spintronic devices.

Perovskite-structured materials host enormous phases such as superconductivity, ferromagnetism, and ferroelectricity, which largely rely on the states of transition metal octahedra. Compared to the extensively studied 3d-orbital perovskite, heavier elements (such as Ta, W, and Ir) with 5d orbitals are of great interest due to their stronger spin–orbital coupling related physics. However, due to the difficulty in synthesis, research on 5d-element perovskite is quite limited. Here, we synthesized tantalate perovskite (Ca,Sr)TaO3 films by pulsed laser deposition. Structural characterizations indicate that the films are epitaxial to the substrates. By tuning the growth parameters such as oxygen partial pressure and growth temperatures, the carrier density can be tuned from ∼1014 to ∼1016 cm−2 while maintaining semiconducting behavior. We found that the interfacial Sr diffusion from the substrate to the film is critical for its structural stabilization. Analogous to KTaO3, our synthesis of (Ca,Sr)TaO3 perovskite films offers a new platform for the study of interfacial physics.

Two-dimensional antiferromagnets that combine the dual advantages of van der Waals (vdW) and antiferromagnetic materials, provide an unprecedented platform to explore emergent spin-related phenomena. However, electrical manipulation of Néel vectors in vdW antiferromagnets —the cornerstone of antiferromagnetic spintronics— remains challenging. Here, we report layer-dependent electrical switching of the Néel vector in an A-type vdW antiferromagnet (Fe, Co)₃GaTe₂ (FCGT) with perpendicular magnetic anisotropy. The Néel vector of FCGT with odd-number vdW layers can be 180° reversed via spin-orbit torques. Furthermore, we achieve field-free switching in an all-vdW, all-antiferromagnet heterostructure of FCGT/CrSBr in which the noncollinear interfacial spin texture breaks the mirror symmetry. Our results establish layer-controlled spin symmetries and interfacial spin engineering as universal paradigms for manipulating antiferromagnetic order, paving the way for realising reliable and efficient vdW antiferromagnetic devices.