Two-Dimensional Materials for Energy-Efficient Spin–Orbit Torque Devices

Abstract

Spin−orbit torques (SOTs), which rely on spin current generation from charge current in a nonmagnetic material, promise an energy-efficient scheme for manipulating magnetization in magnetic devices. A critical topic for spintronic devices using SOTs is to enhance the charge to spin conversion efficiency. Besides, the current-induced spin polarization is usually limited to in-plane, whereas out-of-plane spin polarization could be favored for efficient perpendicular magnetization switching. Recent advances in utilizing two important classes of two-dimensional materialstopological insulators and transition-metal dichalcogenidesas spin sources to generate SOT shed light on addressing these challenges. Topological insulators such as bismuth selenide have shown a giant SOT efficiency, which is larger than those from three-dimensional heavy metals by at least 1 order of magnitude. Transition-metal dichalcogenides such as tungsten telluride have shown a current-induced out-of-plane spin polarization, which is allowed by the reduced symmetry. In this review, we use symmetry arguments to predict and analyze SOTs in two-dimensional material-based heterostructures. We summarize the recent progress of SOT studies based on topological insulators and transition-metal dichalcogenides and show how these results are in line with the symmetry arguments. At last, we identify unsolved issues in the current studies and suggest three potential research directions in this field.

Tuning the High‐Efficiency Field‐Free Current‐Induced Deterministic Switching via Ultrathin PtMo Layer with Mo Content

“…To have better energy efficiency, a material with a large effective θ SHA and high conductivity is very crucial to reduce the current density and energy-efficient of magnetization switching. [23][24][25][26][27] A remarkable progress of manipulating the magnetization has been made towards energy-efficiency scheme using such as alloying HM, [11,28] ferrimagnetic-rearearth transition metal alloy, [29][30] two-dimensional van der Waals materials, [31][32][33] and topological insulators (TIs). [1,27,34] Studies have shown that most TI thin films have limited electrical conductivity in the order of ≈10 5 Ω −1 m −1 , [27,34] which is several times lower than that of HMs and their alloys.…”

Two-Dimensional Van Der Waals Materials for Spin-Orbit Torque Applications

“…Recent years, emerging studies were carried out on 2D SOT devices. Liu et al have summarized the recent progress of SOT studies based on transition-metal dichalcogenides (TMDs) and show how these results are in line with the symmetry arguments (Liu and Shao, 2020). Husain et al reviewed the current progress in research on 2D TMDs for generating SOTs in spin-logic devices (Husain et al, 2020b).…”

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

“…As research interests in SOT devices based on vdW materials have increased, several excellent reviews have summarized recent work of SOT in vdW materials, [ 47 , 52 , 53 , 54 , 55 , 56 , 57 , 58 ] in which nonmagnetic vdW materials, such as, TMDs, TIs, and graphene, are mainly used as the spin current source or spin channel. In addition, magnetic vdW materials appear as promising candidates in SOT devices.…”