Unveiling the potential of spin–orbit torque in a magnetic single layer for advancing spintronics application

Artificial intelligence's rapidly growing computational and storage demands highlight limitations in traditional chip architectures. Spin–orbit torque magnetic random-access memory (SOT-MRAM) is distinguished by its high-speed, high-density, and nonvolatile characteristics. However, conventional SOT devices face efficiency constraints like interfacial spin scattering, limited spin-diffusion lengths, and complexity, driving interest in single-layer SOT switching. Given that research on single-layer SOT systems is still in its early stages and the underlying physical mechanisms remain complex and not fully understood, this review aims to consolidate recent key advances in the field. We categorize deterministic magnetization switching mechanisms via symmetry breaking into three types: global inversion asymmetry of the crystal structure, inversion asymmetry resulting from compositional gradients, and local inversion asymmetry arising from low magnetic symmetry, engineered interface asymmetry, and modified element composition. All three mechanisms can induce SOT in a single-layer film, exerting torque on its magnetic moment to enable efficient magnetization switching. Meanwhile, we highlight the transformative potential of single-layer SOT for next-generation magnetic memory, neural networks, nano-oscillators, and sensors. By critically summarizing switching mechanisms, emerging material platforms, and application potentials, we seek to provide a comprehensive perspective that may inspire the development of next-generation, high-efficiency spintronic applications.