For more than a decade, the electrical switching of ferromagnets (FMs) with perpendicular magnetic anisotropy (PMA), using spin-transfer torque (STT) and more recently spin-orbit torque (SOT), has underpinned the development of fast, low-power-consumption, and high-density spintronic devices. [1][2][3][4][5] In general, both the STT-and the SOT-induced switching of a FM layer require an injection of out-ofplane spin current from nearby layers. [6][7][8] For STT-induced FM switching, particularly, a spin-polarized current is generated in a magnetic tunneling junction structure when a charge current flows perpendicularly through the stacks, where another FM layer acts as a spin polarizer. [9] Thus, device instability issues arise since the tunneling barrier layer between the two FM layers is required to transmit large switching currents.The SOT-induced FM switching, on the other hand, circumvents this problem by using an in-plane switching current. Conventionally, a stack structure consisting of a strong spin-orbit coupling (SOC) layer and a FM layer is used, where an in-plane charge current gives rise to an out-of-plane pure spin current due to spin Hall effect in the SOC layer and/or Rashba effect from the perpendicular interfacial inversion asymmetry. [10][11][12][13] The resulting SOT-induced effective magnetic field is in-plane, hence an additional orthogonal in-plane magnetic field is required to realize deterministic switching of a PMA-FM. To date, several approaches for field-free SOT-induced PMA-FM switching have been proposed and demonstrated, such as switching using a polarized ferroelectric substrate induced in-plane spin current gradient, [14][15][16] a wedge oxide capping layer, [17] a tilted PMA layer, [18] a stack with coherent in-plane exchange field, [19][20][21][22][23] an interplay of SOT and STT, [24,25] an inplane-FM/normal metal/PMA-FM trilayer, [26] and a particular low symmetric WTe 2 semimetal. [27] However, the concomitant complexities of these approaches highlight the inherent limitation of the conventional SOT scheme utilizing external outof-plane spin current injection in a perpendicular asymmetric structure.Here, we demonstrate magnetic field-free deterministic current-induced magnetization switching in a PMA Pt/Co/ Pt trilayer subjected to local laser annealing. Without external magnetic field, the direction of current-induced magnetization switching is found to depend on the relative location and Current-induced magnetization switching by spin-orbit torque (SOT) holds considerable promise for next generation ultralow-power memory and logic applications. In most cases, generation of spin-orbit torques has relied on an external injection of out-of-plane spin currents into the magnetic layer, while an external magnetic field along the electric current direction is generally required for realizing deterministic switching by SOT. Here, deterministic current-induced SOT full magnetization switching by lateral spin-orbit torque in zero external magnetic field is reported. The Pt/Co/Pt magn...

Inspired by ion-dominated synaptic plasticity in the human brain, electronic artificial synapses for neuromorphic computing adopt charge-related quantities as their weights. Despite the existing charge derived synaptic emulating strategies, schemes of controlling electron spins in binary ferromagnetic devices have also attracted considerable interest due to their advantages of low energy consumption, unlimited endurance, and favorable complementary metal-oxide-semiconductor (CMOS) compatibility. However, a generally applicable method of tuning the binary ferromagnet into a multi-state memory with pure spin-dominated synaptic plasticity in the absence of an external magnetic field is still missing. Here, we show how synaptic plasticity of a perpendicular ferromagnetic layer (FM1) can be 2 / 37 obtained when it is interlayer-exchange-coupled by another in-plane ferromagnetic layer (FM2), where a magnetic-field-free current-driven multi-state magnetization switching of FM1 in the Pt/FM1/Ta/FM2 structure is induced by spin-orbit torque. We use current pulses to set the perpendicular magnetization state (represented by the anomalous Hall resistance) which acts as the synapse weight, and demonstrate spintronic implementation of the excitatory/inhibitory postsynaptic potentials and spike timing-dependent plasticity. This functionality is made possible by the action of the in-plane interlayer exchange coupling field which leads to broadened, multi-state magnetic reversal characteristics. Numerical simulations, combined with investigations of a reference sample with a single perpendicular magnetized Pt/FM1/Ta structure, reveal that the broadening is due to the in-plane field component tuning the efficiency of the spin-orbit-torque to drive domain walls across a landscape of varying pinning potentials. The conventionally binary FM1 inside our Pt/FM1/Ta/FM2 structure with inherent inplane coupling field is therefore tuned into a multi-state perpendicular ferromagnet and represents a synaptic emulator for neuromorphic computing, paving a substantial pathway towards the combination of spintronics and synaptic electronics.The source of human memory and learning lies in the plasticity of brain synapses, where the degree of connections between neurons is set by the synaptic strength (or weight), which is much more efficient than conventional computational systems in solving complex problems. 1 Inspired by this, the field of neuromorphic computing, that emulates synaptic learning functions by a single electronic device and then integrates the synaptic devices to neuron circuits, has attracted significant interest, resulting in inspirations in operating principles, algorithms and architectures. 2-4 The demonstration of synapse-like electronic devices are mainly focused on nonvolatile charge memory technologies, including field effect transistors, phase change memory, resistance change memory, ferroelectric switches, etc. These involve manipulating ions and/or Author contributions K.W. conceived and designed the experiments. Y.C. f...

Summary Science, engineering, and medicine ultimately demand fast information processing with ultra-low power consumption. The recently developed spin-orbit torque (SOT)-induced magnetization switching paradigm has been fueling opportunities for spin-orbitronic devices, i.e., enabling SOT memory and logic devices at sub-nano second and sub-picojoule regimes. Importantly, spin-orbitronic devices are intrinsic of nonvolatility, anti-radiation, unlimited endurance, excellent stability, and CMOS compatibility, toward emerging applications, e.g., processing in-memory, neuromorphic computing, probabilistic computing, and 3D magnetic random access memory. Nevertheless, the cutting-edge SOT-based devices and application remain at a premature stage owing to the lack of scalable methodology on the field-free SOT switching. Moreover, spin-orbitronics poises as an interdisciplinary field to be driven by goals of both fundamental discoveries and application innovations, to open fascinating new paths for basic research and new line of technologies. In this perspective, the specific challenges and opportunities are summarized to exert momentum on both research and eventual applications of spin-orbitronic devices.

Spin–orbit torque (SOT) induced perpendicular magnetization switching in Pt1‐xGdx/Co/Al2O3 heterostructure with x = 0, 0.02, 0.14, 0.30, and 0.33 is investigated. With in‐plane charge current flowing through the Pt1‐xGdx layer, field‐free current‐induced magnetization switching is observed for all nonzero x due to the existence of opposite spin Hall angles (θSHA) from Pt1‐xGdx alloys. Furthermore, the large θSHA of about 0.27 is obtained in the optimal Pt0.70Gd0.30 alloy films, which is about four times larger than that of the pure Pt. This work suggests a simple and scalable method for realizing field‐free SOT switching, and provides potential candidates of spin Hall materials that can be used to produce highly efficient SOTs.

No abstract

No abstract

No abstract

Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament J. Appl. Phys. 112, 073303 (2012) Trapping of diffusing germanium by silicon excess co-implanted into fused silica Appl. Phys. Lett. 101, 143107 (2012) Magnetism in MoS2 induced by proton irradiation Appl. Phys. Lett. 101, 102103 (2012) Raman study of the Verwey transition in magnetite at high-pressure and low-temperature: Effect of Al doping