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The electric field manipulates the spin chirality and skyrmion motion direction in a magnetic heterostructure. 

Abstract All-electrical driven magnetization switching attracts much attention in next-generation spintronic memory and logic devices, particularly in magnetic random-access memory (MRAM) based on the spin–orbit torque (SOT), i.e. SOT-MRAM, due to its advantages of low power consumption, fast write/read speed, and improved endurance, etc. For conventional SOT-driven switching of the magnet with perpendicular magnetic anisotropy, an external assisted magnetic field is necessary to break the inversion symmetry of the magnet, which not only induces the additional power consumption but also makes the circuit more complicated. Over the last decade, significant effort has been devoted to field-free magnetization manipulation by using SOT. In this review, we introduce the basic concepts of SOT. After that, we mainly focus on several approaches to realize the field-free deterministic SOT switching of the perpendicular magnet. The mechanisms mainly include mirror symmetry breaking, chiral symmetry breaking, exchange bias, and interlayer exchange coupling. Furthermore, we show the recent progress in the study of SOT with unconventional origin and symmetry. The final section is devoted to the industrial-level approach for potential applications of field-free SOT switching in SOT-MRAM technology. 

Recent advances in using topological insulators (TIs) with ferromagnets (FMs) at room temperature have opened an innovative avenue in spin‐orbit torque (SOT) nonvolatile magnetic memory and low dissipation electronics. However, direct integration of TIs with perpendicularly magnetized FM, while retaining an extraordinary charge‐to‐spin conversion efficiency (>100%), remains a major challenge. In addition, the indispensable thermal compatibility with modern CMOS technologies has not yet been demonstrated in TI‐based structures. Here, high‐quality integration of a perpendicularly magnetized CoFeB/MgO system with TI through a Mo insertion layer is achieved and efficient current‐induced magnetization switching at ambient temperature is demonstrated. The calibrated energy efficiency of TIs is at least 1 order magnitude larger than those found in heavy metals. Moreover, it is demonstrated that the perpendicular anisotropy of the integrated CoFeB/MgO system and the current‐induced magnetization switching behavior are well‐preserved after annealing at>350 °C, offering a wide temperature window for thermal treatments. This thermal compatibility with the modern CMOS back‐end‐of‐line process achieved in these TI‐based structures paves the way toward TI‐based low‐dissipation spintronic applications.