Field-free switching of VG-SOT-pMTJ device through the interplay of SOT, exchange bias, and VCMA effects

Abstract

Field-free magnetization switching via the interplay of spin orbit torque (SOT), exchange bias field (HEX), and voltage controlled magnetic anisotropy (VCMA) is crucial for the development of scalable, high speed, and energy-efficient spintronic memories. This has been experimentally demonstrated by the rapid evolution of the voltage gated-spin orbit torque-magnetic random access memory (VG-SOT-MRAM) cell, in which perpendicular spin current is fed along with the in-plane HEX and VCMA assistance for cell programming. Here, we have examined the writing properties of a three terminal voltage gated-spin orbit torque-perpendicularly magnetized magnetic tunnel junction (VG-SOT-pMTJ) device structure (IrMn/CoFeB/MgO/CoFeB) in-depth through simulation. We observed that SOT critical switching current (I_SOT) decreases either by increasing the VCMA voltage or FL thickness. Even SOT field-like torque can accelerate the switching process and modulate the critical switching current. As the VCMA voltage rises, I_SOT falls by nearly 60%. In our experimental setup, VCMA/SOT optimal pulse width and amplitude for better write delay are 1 ns and 0.3 V, respectively. Furthermore, the impacts of free layer thickness, pMTJ radius, HEX, and noise are analyzed. Finally, we demonstrate the dependency of material parameters on temperature and VCMA voltage.