Magnetic Tunnel Junction Free Layer Segmentation for Stochastic Computing Speed

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Solution Overview

Problem

Magnetic tunnel junction devices have high relaxation times, which limit the operating speed of stochastic computing systems, as existing designs do not effectively manage the thermal stability and magnetization direction of free magnetic layers.

Innovation Solution

The magnetic tunnel junction device incorporates a free magnetic layer with multiple antiferromagnetically coupled layers, each with perpendicular magnetization directions, and a spacer layer configuration that reduces thermal stability and net magnetization, allowing for a lower relaxation time and increased operating speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a magnetic tunnel junction device uses a conventional free magnetic layer with high thermal stability, then data retention is improved, but relaxation time increases and operating speed decreases

Engineering Contradiction:

Improvedata retentionVSAvoidoperating speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The free magnetic layer is divided into multiple sub-layers (first free layer, second free layer, third free layer) with different thermal stability values. This segmentation allows each sub-layer to contribute differently to the overall device performance, enabling simultaneous optimization of data retention and relaxation time through the composite structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the free magnetic layer are assigned different thermal stability characteristics. The first free layer has higher thermal stability for data retention, while the second and third free layers have lower thermal stability to reduce relaxation time. This local differentiation of properties resolves the contradiction between reliability and speed.

Inventive Principle:

Principle #3Local quality

2Strength

If the free magnetic layer has high net magnetization, then magnetic signal strength is improved, but relaxation time increases

Engineering Contradiction:

Improvemagnetic signal strengthVSAvoidrelaxation time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The free magnetic layer is segmented into multiple sub-layers with different magnetization characteristics. The first free layer provides strong magnetic signal, while the second and third free layers are designed with lower magnetization to reduce the overall relaxation time of the device.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The free magnetic layer uses a composite structure of multiple magnetic sub-layers with different properties. This composite approach allows the device to achieve both sufficient magnetic signal strength and reduced relaxation time by combining materials or structures with complementary characteristics.

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 configuration reduces the relaxation time of the magnetic tunnel junction device, enhancing the operating speed of stochastic computing systems by adjusting the thermal stability and net magnetization of the free magnetic layer.

Implementation Method 1

The first free layer and the second free layer may be antiferromagnetically coupled to each other by the spacer layer

Methodology Applied

Scientific EffectAntiferromagnetic coupling: Magnetism

Implementation Method 2

A resistance value of the magnetic tunnel junction device may be changed according to magnetization directions of the two magnetic layers

Methodology Applied

Scientific EffectMagnetic tunneling: Magnetoresistance

Data Source

PatentUS20230111057A1Magnetic tunnel junction device and stochastic computing system including the same

Publication Date: 2023.04.13 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic tunnel junction device includes a pinned magnetic layer, a free magnetic layer, and a tunnel barrier layer between the pinned and free magnetic layers. The free magnetic layer includes a first free layer, a second free layer spaced apart from the tunnel barrier layer with the first free layer therebetween, and a spacer layer between the first free layer and the second free layer. The first free layer and the second free layer are antiferromagnetically coupled to each other by the spacer layer, and each of the first free layer and the second free layer has a magnetization direction substantially perpendicular to an interface between the free magnetic layer and the tunnel barrier layer. A thermal stability of the free magnetic layer is in a range of 0 to 15.