Magnetization switching schemes for nanoscale three-terminal spintronics devices

Abstract

Utilizing spintronics-based nonvolatile memories in integrated circuits offers a promising approach to realize ultralow-power and high-performance electronics. While two-terminal devices with spin-transfer torque switching have been extensively developed nowadays, there has been a growing interest in devices with a three-terminal structure. Of primary importance for applications is the efficient manipulation of magnetization, corresponding to information writing, in nanoscale devices. Here we review the studies of current-induced domain wall motion and spin-orbit torque-induced switching, which can be applied to the write operation of nanoscale three-terminal spintronics devices. For domain wall motion, the size dependence of device properties down to less than 20 nm will be shown and the underlying mechanism behind the results will be discussed. For spin-orbit torque-induced switching, factors governing the threshold current density and strategies to reduce it will be discussed. A proof-ofconcept demonstration of artificial intelligence using an analog spin-orbit torque device will also be reviewed.

Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems

“…SOT in the context of electrical writing in magnetic memories (Fukami and Ohno, 2017;Prenat et al, 2016) is the central topic of this review. The technological relevance of the SOT for the development of the next generation of magnetic random access memories (MRAMs) was pointed out in breakthrough reports by Miron et al, 2011a andLiu et al, 2012b, where they demonstrated SOT switching of the recording magnet.…”

“…The out-of-plane writing current geometry of this more technologically mature switching principle sets physical limitations on efficiency and endurance of the STT-MRAM cell. These can be overcome by the in-plane writing current geometry of the SOT (Fukami and Ohno, 2017;Prenat et al, 2016).…”

“…This eliminates the incubation time. Therefore, the in-plane writing current geometry can make the SOT more efficient and faster than STT (Aradhya et al, 2016;Baumgartner et al, 2017;Fukami and Ohno, 2017;Garello et al, 2014;Prenat et al, 2016).…”

Fast Low-Current Spin-Orbit-Torque Switching of Magnetic Tunnel Junctions through Atomic Modifications of the Free-Layer Interfaces

“…The separate read and write channels in the 3T-MTJ geometry offer additional advantages; faster read-out without read disturbance and lower write energy. While the development of SOT switching has focused primarily on nanoscale perpendicularly magnetized MTJs, their SOT effective-field switching requires much higher currents than can be provided by a reasonably scaled CMOS transistor (current densities in the SH channel are ≥ 1.4 x 10 8 A/cm 2 ) [16], and fast, low write error rate (WER) switching has not yet been demonstrated. Here we report a dramatic performance improvement for in-plane-magnetized 3T-MTJs wherein the strong SOT arising from nano-channels of beta-phase W is combined with two recently discovered effects of Hf atomic layer modifications of the FM-MgO and HM-FM interfaces that, respectively, enhance the interfacial perpendicular magnetic anisotropy energy density [17] and reduce interfacial spin memory loss [18].…”

Electrical Control of Perpendicular Magnetic Anisotropy and Spin‐Orbit Torque‐Induced Magnetization Switching

“…Thus, we can conclude that through controlling the PMA via electrical field driven oxygen ion migration, the spin‐orbit torque induced magnetization switching can be controlled. Furthermore, the memristive behavior that arises from the SOT‐induced multilevel intermediate states due to partial magnetization switching also provides an attractive method for designing multi‐bit data storage43,44 and neuromorphic computing 45–47…”