Bingfeng Miao

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.

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.

Searching for new materials hosting flat bands is pivotal for exploring strongly correlated effects and designing sensitive quantum devices, but remains challenging. We present a general method for realizing flat bands based on mathematical optimization and symmetry analysis. The method enables the discovery of ∼1000 types of two-dimensional lattices that can host flat bands, in sharp contrast with ∼10 flat-band lattices predicted previously besides the well-known ones. We further verify the method using first-principles calculations. Our approach provides new insights for the design of flat-band lattices, particularly when aiming to create experimentally feasible configurations.

The Dzyaloshinskii-Moriya antisymmetric exchange interaction (DMI) stabilises topological spin textures with promising future spintronics applications. According to crystal symmetry, the DMI can be categorized as four different types that favour different chiral textures. Unlike the other three extensively-investigated types, out-of-plane DMI, as the last type that favours in-plane chirality, remained missing so far. Here we apply point-group-dependent DMI matrix analysis to show that out-of-plane DMI exists under reduced crystal symmetry. Through strain and structure engineering, we show how C_s symmetry is realized in ultrathin magnets and observe the out-of-plane DMI stabilised in-plane chirality using spin-polarized electron microscopy. Our results show that extremely low out-of-plane DMI strengths at µeV/atom are sufficient to stabilise topological spin textures, including merons and bimerons. We also demonstrate field-induced reversible control of the in-plane chirality and merons. Our findings open up untapped paths on topological magnetic textures and their potential applications.

Information industry is one of the major drivers of the world economy. Its rapid growth, however, leads to severe heat problem which strongly hinders further development. This calls for a non-charge-based technology. Magnon, capable of transmitting spin information without electron movement, holds tremendous potential in post-Moore era. Given the cornerstone role of the field effect transistor in modern electronics, creating its magnonic equivalent is highly desired but remains a challenge. Here, we demonstrate a nonvolatile three-terminal lateral magnon field effect transistor operating at room temperature. The device consists of a ferrimagnetic insulator (Y₃Fe₅O₁₂) deposited on a ferroelectric material [Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ or Pb(Zr_0.52Ti_0.48)O₃], with three Pt stripes patterned on Y₃Fe₅O₁₂ as the injector, gate, and detector, respectively. The magnon transport in Y₃Fe₅O₁₂ can be regulated by the gate voltage pulses in a nonvolatile manner with a high on/off ratio. Our findings provide a solid foundation for designing energy-efficient magnon-based devices.