Spin‐Orbit Torque in Van der Waals‐Layered Materials and Heterostructures

Abstract

Spin-orbit torque (SOT) opens an efficient and versatile avenue for the electrical manipulation of magnetization in spintronic devices. The enhancement of SOT efficiency and reduction of power consumption are key points for the implementation of high-performance SOT devices, which strongly rely on the spin-orbit coupling (SOC) strength and magnetic properties of ferromagnetic/non-magnetic heterostructures. Recently, van der Waals-layered materials have shown appealing properties for use in efficient SOT applications. On the one hand, transition-metal dichalcogenides, topological insulators, and graphene-based heterostructures possess appreciable SOC strength. This feature can efficiently converse the charge current into spin current and result in large SOT. On the other hand, the newly discovered layered magnetic materials provide ultra-thin and gate-tunable ferromagnetic candidates for high-performance SOT devices. In this review, the latest advancements of SOT research in various layered materials are summarized. First, a brief introduction of SOT is given. Second, SOT studies of various layered materials and heterostructures are summarized. Subsequently, progresses on SOT-induced magnetization switching are presented. Finally, current challenges and prospects for future development are suggested.

All-Electrical Control of Compact SOT-MRAM: Toward Highly Efficient and Reliable Non-Volatile In-Memory Computing

“…Most recently, the FGT system shows the intriguing properties in effective SOT applications because of considerable SOC strength, which can effectively convert the charge current into a spin current, resulting in a larger SOT [22,50]. Briefly, the writing current pulse is injected to the SOC layer during the writing process with the spin current generated due to the spin Hall effect in the SOC layer (e.g., Pt, Ta, and W, etc.)…”

Emerging Low‐Dimensional Heterostructure Devices for Neuromorphic Computing

“…[32] Not limited to thick switching materials, recent works show that the atomically thin heterostructure devices exhibit memristive switching behaviors, which can be extended to a library of 2D materials and van der Waals (vdW) heterostructures. [36,39,40] Spintronic devices based on the low-dimensional heterostructures [19,41,42] are also promising for neuromorphic computing. [22,[43][44][45][46][47][48] Magnetic tunnel junction based on ferromagnetic metal/oxide/ferromagnetic metal heterostructure has been regarded as one of promising candidates for nonvolatile memory and computing applications.…”

“…[22,[43][44][45][46][47][48] Magnetic tunnel junction based on ferromagnetic metal/oxide/ferromagnetic metal heterostructure has been regarded as one of promising candidates for nonvolatile memory and computing applications. [41,[49][50][51] Magnetization dynamics in the spin-torque oscillators based on magnetic tunnel junction gives rise to nonlinear I-V characteristics and finite magnetization relaxation time and have been employed to implement reservoir computing. [52,53] Moreover, by utilizing spin-transfer torque and magnetoresistive effect, neuromorphic neural network can be implemented.…”

“…Spintronic devices based on the low‐dimensional heterostructures [ 19,41,42 ] are also promising for neuromorphic computing. [ 22,43–48 ] Magnetic tunnel junction based on ferromagnetic metal/oxide/ferromagnetic metal heterostructure has been regarded as one of promising candidates for nonvolatile memory and computing applications.…”

Electric Control of Exchange Bias Effect in FePS3–Fe5GeTe2 van der Waals Heterostructures

“…As a long time pursuit for spintronics applications, electrical gate-manipulated EB effects in AFM–FM structures enable scalable energy-efficient spin–orbit logic, which is very promising for beyond-COMS devices in future low energy electronic technologies . To date, only very limited electrically tunable EB effects have been experimentally demonstrated, and most of them have been based on oxide multiferroic thin film systems. − The recent emergence of van der Waals (vdW) heterostructures − and the discovery of 2D ferromagnetism , have enabled various studies on vdW magnetic and spintronic devices. − The high-quality interfaces and weak interlayer coupling observed in vdW magnetic heterostructures so far suggest opportunities to explore intrinsically interfacial magnetic coupling mechanisms. This is in contrast to coupling in traditionally grown thin films, which tends to be governed largely by interfacial defects. − Despite EB effects being extensively investigated in vdW magnets and AFM–FM heterostructures, − an electrically tunable EB effect in vdW AFM–FM heterostructures has yet to be realized.…”