Chain of magnetic tunnel junctions as a spintronic memristor

Abstract

In the context of neuromorphic computation, spintronic memristors are investigated for their use as synaptic weights. In this paper, we propose and experimentally demonstrate a resistive synaptic device based on ten magnetic tunnel junctions (MTJs) connected in a serial configuration. Our device exhibits multiple resistance levels, that supports its use as a synaptic element. It allows for two operating knobs: external magnetic field and voltage pulses (Spin-Transfer Torque). Moreover, it can be operated in different ways. When varying continuously the amplitude of the voltage pulse and/or the magnetic field, eleven resistance states can be reached. In contrast, if the initial state of the chain is reset between every step, a very large number of levels are reached. Ideally, a total of 2 N resistance levels could be accessible. This coincides well with the desired analog-like behavior in ideal memristors. Since this device consists of a scalable number of N MTJs, and MTJ technology is continuously optimized and improved, the proposed memristor shows promise as a scalable synapse solution for neuromorphic hardware implementations.

Multi‐Level Switching and Reversible Current Driven Domain‐Wall Motion in Single CoFeB/MgO/CoFeB‐Based Perpendicular Magnetic Tunnel Junctions

“…Up to date, the efforts on multi-level switching in MTJs have mainly focused on fabricating one MTJ on top of the other, [10,11] or connecting several MTJs in series. [12,13] The former results in complex process of manufacture, while the latter cannot increase the storage density efficiently. A practical implementation of multi-level switching in single p-MTJ can offer a better solution.…”

Spintronic memristors for neuromorphic circuits based on the angular variation of tunnel magnetoresistance

“…We note that the oscillation frequencies extracted turn out to be significantly lower than the GHz range. This is likely the result of the important increase of the Gilbert damping already observed in FM/AF bilayers 29,30 as well as FM/AF/FM trilayers 31 (6) from ref 12 , where 𝜃 𝑀 is the magnetization polar angle. The linear behavior of this last equation with respect to the applied voltage can be used to fit the experimental points as in Fig.…”

Heavy-Ion Irradiation Effects on Advanced Perpendicular Anisotropy Spin-Transfer Torque Magnetic Tunnel Junction

“…The present work differs from the previous since it intends to be a preliminary study to the integration of these spintronic devices with the most advanced CMOS node. If the robustness to high LET is confirmed, one suitable strategy for future design could be to replace as many transistors as possible with magnetic devices, using the logic in memory concepts based on purely magnetic logic gate [12]. This work is organized mainly in two levels: in one hand, at stack level, it is focused on the radiation-induced effects on the atomic structure of a PA-STT film; on the other hand, at device level, to the Single Event Effect (SEE) on purely magnetic PA-STT memory arrays that are programmed by the use of an external board instead of peripheral CMOS circuit.…”