Synergizing intrinsic symmetry breaking with spin–orbit torques for field-free perpendicular magnetic tunnel junction

Abstract

Current-induced spin–orbit torque (SOT) facilitates the ultrafast electrical manipulation of magnetic tunnel junction (MTJ), which is a leading non-volatile technology for the microelectronic industry. The key bottleneck to the commercial application of SOT-MTJ is the absence of a practicable symmetry-breaking scheme to switch perpendicular magnetization without an external magnetic field. Here, we demonstrate the wafer-scale realization of internalized field-free switching in perpendicular SOT-MTJ using conventional materials and device structure. We utilize a dual-function tungsten (W) spacer, which generates sizable SOT while concomitantly breaking symmetry via interlayer exchange coupling (IEC). Tuning the W thickness enables field-free switching with two types of IEC. An optimized combination of SOT and IEC ensures competitive switching performance, with our device exhibiting excellent thermal stability, low switching current density, and fast operating speed. This work builds the long-sought bridge between SOT manipulation of magnetization and wafer-scale field-free perpendicular MTJ. It underscores the urgent need to incorporate perpendicular SOT-MTJ in integrated circuits for applications in logic, memory, and unconventional computing.