Spin-Transfer Torque Magnetic Memory as a Stochastic Memristive Synapse for Neuromorphic Systems

Abstract

Spin-transfer torque magnetic memory (STT-MRAM) is currently under intense academic and industrial development, since it features non-volatility, high write and read speed and high endurance. In this work, we show that when used in a non-conventional regime, it can additionally act as a stochastic memristive device, appropriate to implement a "synaptic" function. We introduce basic concepts relating to spin-transfer torque magnetic tunnel junction (STT-MTJ, the STT-MRAM cell) behavior and its possible use to implement learning-capable synapses. Three programming regimes (low, intermediate and high current) are identified and compared. System-level simulations on a task of vehicle counting highlight the potential of the technology for learning systems. Monte Carlo simulations show its robustness to device variations. The simulations also allow comparing system operation when the different programming regimes of STT-MTJs are used. In comparison to the high and low current regimes, the intermediate current regime allows minimization of energy consumption, while retaining a high robustness to device variations. These results open the way for unexplored applications of STT-MTJs in robust, low power, cognitive-type systems.

Spintronic Nanodevices for Bioinspired Computing

“…Recent simulations [92] explore the capability of magnetic tunnel junctions for stochastic STDP. This work shows that a system equipped with magnetic tunnel junctions implementing a highly abstracted form of stochastic STDP can learn complex tasks such as detecting cars in a video (Fig.…”

Interplay of multiple synaptic plasticity features in filamentary memristive devices for neuromorphic computing

“…Because input and output spikes have exact opposite waveforms, the learning rule is fully driven by the relative timings of the spikes received by the synapses. This embedded learning rule is therefore especially interesting from the CMOS circuitry point of view: the programming events have simple waveforms, and no external control circuit but neurons are required to implement the learning rule, contrary to systems that use other types of memristors3536.…”

Исследование Связанной Динамики Магнитных Вихрей В Трехслойном Проводящем Наноцилиндре

“…Оно содержит дополнительный вращательный момент T s .t. [1], ответ-ственный за взаимодействие тока с намагниченностью, и имеет следующий вид:…”

“…В настоящее время большое внимание привлекают исследования переключения и возбуждения осцилляций намагниченности в магнитных наноструктурах с по-мощью спин-поляризованного тока [1][2][3], которые мо-гут позволить увеличить скорости жестких дисков и устройств магнитной памяти, вплоть до терагерцового уровня. Интересны в этом плане и микроволновые спин-трансферные наноосцилляторы (СТНО), которые отличаются относительно большим спектром частот осцилляций магнитных вихрей, реализуемых даже без приложения внешнего магнитного поля.…”