Shaohua Fan

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.

The structure, intrinsic magnetic properties, and domain structure of Sm0.7Zr0.3(Fe0.75Co0.25)11.5M0.5 (M = Ti, Mo) compounds were systematically investigated using neutron diffraction, magnetic measurements, magneto-optical Kerr effect, and first-principles calculations. The results demonstrate that the ThMn12-type structure is co-stabilized by substituting Zr for Sm at the 2a site and M for Fe at the 8i site. The effect of M substitution on the electronic band structure can be explained by the rigid band model, where the d–d electron-orbital hybridization between M and Fe leads to a negative effect on the Fe local magnetic moment. Besides, M changes the magnetic anisotropy by altering the electronic density surrounding Sm. Both the compounds exhibit higher Curie temperatures and magnetocrystalline anisotropy fields compared to the well-known Nd2Fe14B magnet, with Tc and μ0Ha reaching 819.3 K and 9.23 T for M = Ti, and 820.0 K and 8.41 T for M = Mo, respectively. The relevant magnetic domain parameters also indicate that these compounds have significant potential for the development of permanent magnet materials.

Surface modification of metallic magnetic powders is important to regulate high-frequency electromagnetic properties for microwave absorbing composite materials composed of these powders and insulating media. In this study, atomic layer deposition (ALD) was applied to coat metallic magnetic Y2Fe16Si powder with uniform Al2O3 layer to improve its high-frequency electromagnetic properties. The thickness of the coating layer was characterized by transmission electron microscopy and x-ray photoelectron spectroscopy methods, with an average value of approximately 50 nm. It was found that the coating layer can significantly decrease the permittivity, and hence improve the impedance matching and the microwave absorption capability of the Y2Fe16Si@Al2O3–paraffin composite. A high reflection loss of −63 dB was achieved at 9.9 GHz with a thickness of 2.2 mm, and an effective absorption bandwidth of 6.4 GHz was obtained at 1.6 mm. This study demonstrates the potential of ALD technology for optimizing the electromagnetic properties of metallic magnetic powder materials for better microwave absorption.