A four-state magnetic tunnel junction switchable with spin–orbit torques

Abstract

We present a magnetic tunnel junction (MTJ) where its two ferromagnetic layers are in the form of a single ellipse (SE) and two-crossing ellipses (TCEs). The MTJ exhibits four distinct resistance states corresponding to the four remanent states of the TCE structure. Flowing current in an underlying Ta layer generates in the adjacent TCE structure spin–orbit torques, which induce field-free switching of the four-state MTJ between all its resistance states. The demonstrated four-state MTJ is an important step toward fabricating multi-level MTJs with numerous resistance states, which could be important in various spintronics applications, such as multi-level magnetic random access or neuromorphic memory.

Volatile and Nonvolatile Memristive Devices for Neuromorphic Computing

“…The STT-based neurons can faithfully simulate the bioneuron behaviors, thus, the ANNs or SNNs can be realized on STT-based memristive systems. [145][146][147][148][149][150]…”

Implementation of Highly Reliable and Energy‐Efficient Nonvolatile In‐Memory Computing using Multistate Domain Wall Spin–Orbit Torque Device

“…Some of the reported multistate realizations are based on in-plane magnetic anisotropic structures or geometric device fabrications with domain wall motion (DWM) models, e.g., the experimental demonstration of the two-level device based on DWM in a spin valve, [38] three-level device with the half-ring shape, [39] and four-state MTJ switchable with SOT. [40] Despite the available reports on pure simulation and prototype DW-MTJ devices, [8,[41][42][43][44][45] development is hindered by system integration and operation efficiency limits. Explicitly, to date, few functional implementations exist of SOT-MTJ devices with reliable and switchable multistates in a synthetic, CMOS compatible, and field-free integration.…”