Hai Feng Ding

Chiral spin textures, largely driven by the Dzyaloshinskii–Moriya interaction, offer significant potential for next‐generation computing technologies due to their chirality and topological stability. Ferroelectric/ferromagnetic van der Waals heterostructures are particularly appealing because they can combine interfacial inversion‐symmetry breaking and spin‐orbit coupling to promote interfacial Dzyaloshinskii–Moriya interaction, while switchable ferroelectric polarization provides a nonvolatile tuning knob. This study investigates interfacial chiral spin textures in few‐layer /‐ heterostructures. Two groups of topological Hall signals are identified just below and above the coercive field, and thickness‐dependent transport reveals a notable reduction in critical temperature with increasing layer thickness. Low‐temperature magnetic force microscopy images reveal two types of magnetic bubbles with opposite magnetic contrasts near the coercive field, each associated with distinct topological Hall signals. Together with atomistic spin‐dynamics simulations and first‐principles calculations, these results support the formation of interfacial DMI‐stabilized chiral spin textures. Switching the ferroelectric polarization of the ‐ layer further enables nonvolatile modulation of both anomalous and topological Hall effects. The resulting ferroelectric and magnetic bistabilities generate four distinguishable Hall resistance states programmable by electric and magnetic fields. These findings highlight the potential of van der Waals interfaces for advanced device applications.

Spin-orbit torque magnetic random-access memory is a promising next-generation non-volatile memory technology featuring low power consumption, rapid operation, and high endurance. Conventional spin-orbit torque-induced deterministic perpendicular magnetization switching, however, typically requires the assistance of an external magnetic field. While multiple field-free switching strategies have been demonstrated, most suffer from significant limitations. Here, we present a straightforward and reliable approach for field-free switching of perpendicular magnetization utilizing two orthogonal electrical currents. The method employs only conventional heavy metals as spin current sources and enables seamless integration into existing manufacturing lines as it is fully compatible with standard fabrication processes for commercialized spin-transfer torque magnetic random-access memory. Notably, the approach also achieves ultrafast magnetization switching with robust immunity against external magnetic fields along all directions.

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.

The rise of the 2D ferromagnets not only significantly advances fundamental physics and materials science but also provides excellent opportunities for various applications, particularly in spintronics. The 2D ferromagnets reported so far either show a Curie temperature ( T _c ) below room temperature (RT) or possess a high magnetic damping ( α ), which strongly limits their applications. Here, utilizing a state‐of‐the‐art interconnected molecular beam epitaxy and magnetron sputtering system, we fabricate high‐quality self‐intercalated Cr _1.8 Te ₂ films and Cr _1.8 Te ₂ /Pt heterostructures with clean interfaces. We find that the Cr _1.8 Te ₂ simultaneously achieves a high T _c (∼340 K) and a record‐low α (∼0.02) among all 2D ferromagnets with T _c exceeding RT. These unique features enable the first observation of spin injection from a 2D ferromagnet via spin pumping in Cr _1.8 Te ₂ /Pt bilayers under ambient conditions. Our findings establish self‐intercalated Cr _1.8 Te ₂ as an efficient spin current source at RT, highlighting its great potential for practical spintronic applications.

Hexagonal boron nitride (hBN), an insulating two-dimensional (2D) material, is widely regarded as an ideal dielectric layer for 2D-based functional devices. Nevertheless, achieving wafer-scale ultra-flat hBN films with uniform thickness and high insulating properties remains a significant challenge. Here, we demonstrate the controlled growth of ultra-flat hBN single-crystal wafers with well-defined layer numbers tuned from one to eight. These hBN films are crystallized from amorphous precursors with predefined thickness, resulting in ultra-flat surfaces, uniform AA’ stacking order and single-crystal features. These ultra-flat films demonstrate excellent insulating performances across the entire wafer, with breakdown fields of 10 – 12 MV/cm and leakage current densities below 10-13 A/cm2. They can be directly employed as dielectric layers for high-performance graphene electronic devices. These highly insulating, wafer-scale ultra-flat hBN wafers will further accelerate the next-generation 2D-based multifunctional devices.

Magnetic skyrmionic structures, including magnetic skyrmions and antiskyrmions, are characterized by swirling spin textures with non-trivial topologies. They are featured with specific topological charges, Q, which are of crucial importance in determining their topological properties. Owing to the invariance of the chiral nature, it is generally believed that Q is conserved in a given magnetic skyrmionic structure and is hard to alter. Here, we experimentally realize the control of Q of magnetic skyrmionic structures at room temperature in a Dzyaloshinskii-Moriya interaction (DMI) platform with spatially alternating signs. Depending on how many times it crosses the interfaces between DMI regions with opposite signs, the magnetic skyrmionic structures possess different Q. Modifying the DMI energy landscape through chemisorbed oxygen, a magnetic topological transition is realized. This creation and manipulation of magnetic skyrmionic structures with controllable Q, in particular the DMI-stabilized thin-film antiskyrmions and high-Q skyrmionic structures, enables a new degree of freedom to control their dynamics via a novel DMI confinement effect. Our findings open up an unexplored avenue on various topological magnetic skyrmionic structures and their potential applications.