Since the experimental discovery of magnetic skyrmions achieved one decade ago 1 , there have been significant efforts to bring the virtual particles into all-electrical fully functional devices, inspired by their fascinating physical and topological properties suitable for future low-power electronics 2 . Here, we experimentally demonstrate such a deviceelectrically-operating skyrmion-based artificial synaptic device designed for neuromorphic computing. We present that controlled current-induced creation, motion, detection and deletion of skyrmions in ferrimagnetic multilayers can be harnessed in a single device at room temperature to imitate the behaviors of biological synapses. Using simulations, we demonstrate that such skyrmion-based synapses could be used to perform neuromorphic pattern-recognition computing using handwritten recognition data set, reaching to the accuracy of ~89%, comparable to the software-based training accuracy of ~94%. Chip-level simulation then highlights the potential of skyrmion synapse compared to existing technologies. Our findings experimentally illustrate the basic concepts of skyrmion-based fully functional electronic devices while providing a new building block in the emerging field of spintronics-based bio-inspired computing.

Since the discovery of ferromagnetic two-dimensional (2D) van der Waals (vdW) crystals, significant interest on such 2D magnets has emerged, inspired by their appealing physical properties and integration with other 2D family for unique heterostructures. In known 2D magnets, spin-orbit coupling (SOC) stabilizes perpendicular magnetic anisotropy down to one or a few monolayers. Such a strong SOC could also lift the chiral degeneracy, leading to the formation of topological magnetic textures such as skyrmions through the Dzyaloshinskii-Moriya interaction (DMI). Here, we report the experimental observation of Néel-type chiral magnetic skyrmions and their lattice (SkX) formation in a vdW ferromagnet Fe 3 GeTe 2 (FGT). We demonstrate the ability to drive an individual skyrmion by short current pulses along a vdW heterostructure, FGT/h-BN, as highly required for any skyrmion-based spintronic device. Using first principle calculations supported by experiments, we unveil the origin of DMI being the interfaces with oxides, which then allows us to engineer vdW heterostructures for desired chiral states. Our finding opens the door to topological spin textures in the 2D vdW magnet and their potential device application.

Spintronic devices based on magnetic skyrmions are a promising candidate for nextgeneration memory applications due to their nanometre-size, topologically-protected stability and efficient current-driven dynamics. Since the recent discovery of roomtemperature magnetic skyrmions, there have been reports of current-driven skyrmion displacement on magnetic tracks and demonstrations of current pulse-driven skyrmion generation. However, the controlled annihilation of a single skyrmion at room temperature has remained elusive. Here we demonstrate the deterministic writing and deleting of single isolated skyrmions at room temperature in ferrimagnetic GdFeCo films with a device-compatible stripline geometry. The process is driven by the application of current pulses, which induce spin-orbit torques, and is directly observed using a time resolved nanoscale X-ray imaging technique. We provide a current-pulse profile for the efficient and deterministic writing and deleting process. Using micromagnetic simulations, we also reveal the microscopic mechanism of the topological fluctuations that occur during this process.Nanoscale memory devices that employ magnetic materials and offer non-volatility and efficient electrical controllability have the potential to outperform and eventually replace conventional silicon-based memory technologies such as DRAM or NAND-Flash 1-3 . Among the many different types of spintronic memory devices available, those based on magnetic skyrmions -topologically non-trivial spin nanostructures -are of particular interest. 4-10 Key advantages of skyrmion-based memory device include their stability 9 , high-density arrangement 4,5 and low-power operation using electrical excitations 6-8 . Recently the room-temperature stabilization of magnetic skyrmions and their current pulse-induced displacement on nanotracks has been reported in magnetic heterostructures such as Ta/CoFeB/MgO 11,12 , Pt/Co/Ta 13 , Pt/CoFeB/MgO 13-15 , Pt/Co/Ir 16 and Pt/GdFeCo/MgO 17 where the strong interfacial Dzyaloshinskii-Moriya interaction (DMI)leads to the stabilization of the skyrmion structures 18,19 . While such current-controlled skyrmion motion is applicable to an actual device scheme, the deterministic writing and deleting of a single isolated magnetic skyrmion at room temperature is required for fully functional skyrmionic devices 10,20 .Theoretical studies have suggested that skyrmions can be created by applying localized vertical spin-polarized current to a confined geometry 21 or well-defined notches 22 .Moreover, there are suggestions that a single skyrmion can be formed by the conversion of a pair of domain walls 23,24 . However, the controlled creation of a single skyrmion, and the subsequent annihilation of the same skyrmion, has only been experimentally achieved at low temperatures with spin-polarized scanning tunneling microscopy (SP-STM) 8,25 . This approach requires the in situ deposition of material at cryogenic conditions, which may be hard to incorporate into actual commercial devices. Recently, several s...

Magnetic skyrmions are topologically protected spin textures with attractive properties suitable for high-density and low-power spintronic device applications. Much effort has been dedicated to understanding the dynamical behaviours of the magnetic skyrmions. However, experimental observation of the ultrafast dynamics of this chiral magnetic texture in real space, which is the hallmark of its quasiparticle nature, has so far remained elusive. Here, we report nanosecond-dynamics of a 100nm-diameter magnetic skyrmion during a current pulse application, using a time-resolved pump-probe soft X-ray imaging technique. We demonstrate that distinct dynamic excitation states of magnetic skyrmions, triggered by current-induced spin–orbit torques, can be reliably tuned by changing the magnitude of spin–orbit torques. Our findings show that the dynamics of magnetic skyrmions can be controlled by the spin–orbit torque on the nanosecond time scale, which points to exciting opportunities for ultrafast and novel skyrmionic applications in the future.