Magnetoresistive Memristor Using Spin Transfer for Neural Networks

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Solution Overview

Problem

Existing neuromimetic circuits on chips face challenges with high operating temperatures and low operating speed due to ion electromigration effects in traditional memristors, limiting their ability to simulate synaptic plasticity effectively.

Innovation Solution

A magnetoresistive memristor is developed using spin transfer to displace a magnetic wall, allowing for adjustable resistance within a continuous range, with electrodes applied to polarized current to control the magnetic wall's movement, enabling quick and high-value resistance adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If ion electromigration effect is used in traditional memristors, then resistance can be adjusted, but operating temperature becomes high and operating speed becomes low

Engineering Contradiction:

Improveresistance adjustment capabilityVSAvoidoperating speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The patent replaces the ion electromigration mechanism (chemical/physical process) with spin transfer torque mechanism (magnetic process). The spin-polarized current exerts torque on the magnetic moment to move the magnetic wall, achieving resistance adjustment without ion migration. This substitution eliminates the need for high temperatures and enables much faster operation speeds.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental operating parameter from ion migration-driven resistance change to spin-transfer-driven magnetic wall movement. By controlling the spin-polarized current density and duration, the magnetic wall position can be precisely controlled, achieving continuous resistance adjustment within a wide range while operating at much higher speeds and lower temperatures.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If ion electromigration effect is used in traditional memristors, then resistance can be adjusted, but operating temperature becomes high causing potential device fragility

Engineering Contradiction:

Improveresistance adjustment capabilityVSAvoidoperating temperature

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The patent replaces the ion electromigration mechanism (thermal process) with spin transfer torque mechanism (magnetic process). The spin-polarized current exerts torque on the magnetic moment to move the magnetic wall, achieving resistance adjustment without ion migration. This substitution eliminates the need for high temperatures and enables much faster operation speeds.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If spin valve is used to create memristor, then resistance can be adjusted, but magnetoresistance is low (order of 10%) making resistance values very low

Engineering Contradiction:

Improveresistance adjustment capabilityVSAvoidresistance value range

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent uses a composite magnetic structure consisting of a first magnetic layer, a non-magnetic spacer layer, and a second magnetic layer. This composite structure enables the formation of a magnetic wall that can be moved by spin transfer torque, achieving high magnetoresistance ratios (up to 1000%) and wide resistance adjustment range while maintaining reliable operation.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution provides a memristor with rapid resistance adjustment capabilities, reducing the risk of component damage and achieving sub-micrometer size adjustments in nanoseconds, while maintaining low current densities, thus overcoming the limitations of traditional memristors.

Implementation Method 1

A magnetoresistive memristor is developed using spin transfer to displace a magnetic wall

Methodology Applied

Scientific EffectSpin transfer:

Implementation Method 2

The invention is based on the magnetoresistance effect, more precisely on the tunnel magnetoresistance effect, which is the variation of resistance of a magnetic structure in function of the relative orientation of the magnetization of two magnetic layers

Methodology Applied

Scientific EffectTunnel magnetoresistance: Magnetoresistance

Data Source

PatentEP2425434B1Memristor device with resistance adjustable by moving a magnetic wall by spin transfer and use of said memristor in a neural network.

Publication Date: 2016.01.27 THALES SA

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AI summary

The present invention relates to a device with adjustable resistance comprising two magnetic elements (FM1, FM2) separated by an insulating or semi-conductor element (I). The resistance of the device depends on the position of a magnetic wall in one of the magnetic elements, the magnetic wall separating two areas of said magnetic element each having a separate homogeneous direction of magnetisation. The device comprises a means (4) for moving the magnetic wall in the magnetic element by applying a spin polarised electric current, such that the resistance of the device is adjustable in a continuous range of values. The invention is useful in neuromimetic circuits, neural networks and bio-inspired computers.