Spin-orbit torque (SOT) provides an ultrafast and energy-efficient means to switch magnetization, which is of fundamental and technical importance for spintronic devices. [1][2][3][4][5] A typical SOT device consists of heavy metal/ferromagnet (HM/FM) bilayer, where the HM (e.g., Pt, W, Ta, etc.) converts charge current into spin current mainly due to the spin Hall effect (SHE) and then exerts a torque on the adjacent FM enabling magnetization manipulation. To improve the energy efficiency of SOT-driven magnetization switching, considerable efforts have been made to enhance the charge-spin conversion efficiency of HM [6][7][8][9] and reduce the shunting current in the FM. [10,11] Engineering the bilayer structure [9,12] or replacing HM by novel materials with larger charge-spin conversion efficiency and higher conductivity [10,13,14] are possible avenues to realize higher SOT efficiency. Manipulation of magnetization by electric-current-induced spin-orbit torque (SOT) is of great importance for spintronic applications because of its merits in energy-efficient and high-speed operation. An ideal material for SOT applications should possess high charge-spin conversion efficiency and high electrical conductivity. Recently, transition metal dichalcogenides (TMDs) emerge as intriguing platforms for SOT study because of their controllability in spin-orbit coupling, conductivity, and energy band topology. Although TMDs show great potentials in SOT applications, the present study is restricted to the mechanically exfoliated samples with small sizes and relatively low conductivities.Here, a manufacturable recipe is developed to fabricate large-area thin films of PtTe 2 , a type-II Dirac semimetal, to study their capability of generating SOT. Large SOT efficiency together with high conductivity results in a giant spin Hall conductivity of PtTe 2 thin films, which is the largest value among the presently reported TMDs. It is further demonstrated that the SOT from PtTe 2 layer can switch a perpendicularly magnetized CoTb layer efficiently. This work paves the way for employing PtTe 2 -like TMDs for wafer-scale spintronic device applications.

M agnetic   skyrmions are particle-like spin textures that have been observed in chiral bulk magnets 1-4 and asymmetric magnetic multilayers 5-14. Electrical currents and current-induced spin-orbit torques (SOTs) can be used to manipulate skyrmions in various metallic systems 2,7,8,10,14 , and such capabilities could be useful in the development of energy-efficient spintronic devices. Thermal effects can also be used to generate and manipulate skyrmions 15,16 , which could lead to the development of unconventional computing 17 and energy-harvesting 18 applications. These thermal effects are, however, difficult to observe in bulk samples and large-area films; therefore, microstructured devices need to be employed. Furthermore, the generation of skyrmions via a pure thermal effect 19-21 has not been experimentally demonstrated so far; moreover, whether the skyrmion motion driven by thermal gradients follows the direction of thermal diffusion or, oppositely, the direction of magnonic spin torque 15,20,22,23 remains an open question.   approach allows us to study the dynamics of skyrmions induced by a perpendicular magnetic field (μ 0 H ⊥), electrical current (j e), temperature (T) and temperature gradient (ΔT(x)). The magnetic imaging was conducted at the Fe L 3 edge Q6

We demonstrate spin-orbit torque (SOT) switching of amorphous CoTb single layer films with perpendicular magnetic anisotropy (PMA). The switching sustains even the film thickness is above 10 nm, where the critical switching current density keeps almost constant. Without the need of overcoming the strong interfacial Dzyaloshinskii-Moriya interaction caused by the heavy metal, a quite low assistant field of ~20 Oe is sufficient to realize the fully switching. The SOT effective field decreases and undergoes a sign change with the decrease of the Tb-concentration, implying that a combination of the spin Hall effect from both Co and Tb as well as an asymmetric spin current absorption accounts for the SOT switching mechanism. Our findings would advance the use of magnetic materials with bulk PMA for energy-efficient and thermal-stable non-volatile

Spintronic devices are considered a possible solution for the hardware implementation of artificial synapses and neurons, as a result of their non-volatility, high scalability, complementary metal-oxide-semiconductor transistor compatibility, and low power consumption. As compared to ferromagnets, ferrimagnet-based spintronics exhibits equivalently fascinating properties that have been witnessed in ultrafast spin dynamics, together with efficient electrical or optical manipulation. Their applications in neuromorphic computing, however, have still not been revealed, which motivates the present experimental study. Here, by using compensated ferrimagnets containing Co 0.80 Gd 0.20 with perpendicular magnetic anisotropy, it is demonstrated that the behavior of spin-orbit torque switching in compensated ferrimagnets could be used to mimic biological synapses and neurons. In particular, by using the anomalous Hall effect and magneto-optical Kerr effect imaging measurements, the ultrafast stimulation of artificial synapses and neurons is illustrated, with a time scale down to 10 ns. Using experimentally derived device parameters, a threelayer fully connected neural network for handwritten digits recognition is further simulated, based on which, an accuracy of more than 93% could be achieved. The results identify compensated ferrimagnets as an intriguing candidate for the ultrafast neuromorphic spintronics.

The explosive demands of storage capacity and the von Neumann bottleneck of modern computer architectures trigger many innovations in information technology. Amongst them, nonvolatile spintronics attract considerable attentions for which can embed the computation capability into memory, enable neuromorphic, and probabilistic computing. These exciting progresses typically rely on the manipulation of the relative magnetization orientations of two magnetic layers. By extending to 3D spintronic architectures made of multiple magnetic layers (n), the exponentially increased 2n magnetic states can provide ample opportunities for implementing novel spintronic functionalities. Here, through building perpendicularly magnetized 3D spin‐orbitronic architectures – [Pt/Fe1−xTbx/Si3N4]n multilayers, it is demonstrated the electrical programing of 2n memory states via current‐induced spin–orbit torques (SOTs), and the accompanied reconfigurable multifunction in‐memory logic features in a single four‐terminal Hall device. Further, an electrical readout of these 2n states, together with the implementation of Boolean logic gates and digital circuitry such as 2–4 and 3–8 decoders, are successfully conducted. More complex logic circuits are also envisioned. The experiments thus substantiate 3D spin‐orbitronic structures as a promising platform for exponentially boosting the storage capacity and accommodating in‐memory computing that can be important for promoting the emerging 3D nanospintronics.

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The discovery of magnetic skyrmions provides a promising pathway for developing functional spintronic memory and logic devices. Towards the future high-density memory application, nanoscale skyrmions with miniaturized diameters, ideally down to 20 nm are required. Using x-ray magnetic circular dichroism transmission microscopy, nanoscale skyrmions are observed in the [Pt/Co/Ir]15 multilayer at room temperature. In particular, small skyrmions with minimum diameters approaching 20 nm could be generated by the current-induced spin-orbit torques. Through implementing material specific parameters, the dynamic process of skyrmion generation is further investigated by performing micromagnetic simulations. According to the simulation results, we find that both the tube-like Néel-type skyrmions and the bobber-like Néel-type skyrmions can be electrically generated. In particular, the size of the bobber-like Néel-type skyrmions can be effectively reduced by the spin-orbit torques, which leads to the formation of 20 nm Néel-type skyrmions. Our findings could be important for understanding the formation dynamics of nanoscale Néel-type spin textures, skyrmions and bobber in particular, which could also be useful for promoting nanoscale skyrmionic memories and logic devices.

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