Graphene Magnetic Tunnel Junction with Segmented Potentials

Solution Overview

Problem

Current magnetic tunnel junctions have limitations in achieving high tunnel magnetoresistance (TMR) ratios, which affect the sensitivity and performance of hard disk read heads and magnetic field sensors, particularly in requiring low temperatures for optimal operation.

Innovation Solution

A graphene-based magnetic tunnel junction with segmented potentials is designed, featuring a periodic graphene nanoribbon layer with alternating potential segments between the pinned and free layers, enhancing the TMR ratio to 107%.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single-barrier structure is used in magnetic tunnel junctions, then the device structure is simple, but the TMR ratio is limited to about 102%

Engineering Contradiction:

Improvestructure complexityVSAvoidTMR ratio

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The barrier is divided into multiple segments with different materials and potential heights, creating a multi-barrier structure. This segmentation allows each barrier segment to contribute differently to the tunneling process, enabling the TMR ratio to reach about 103% while managing structural complexity through systematic design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite barrier structures combining different insulating materials (such as Al2O3, MgO, Ta2O5) with varying thicknesses and potential heights. This composite approach leverages the advantageous properties of each material to achieve enhanced TMR ratio of 107% through constructive interference of tunneling electrons.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a double-barrier structure is used in magnetic tunnel junctions, then the TMR ratio can reach about 103%, but the device structure becomes more complex

Engineering Contradiction:

ImproveTMR ratioVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The barrier is divided into multiple segments with different materials and potential heights, creating a multi-barrier structure. This segmentation allows each barrier segment to contribute differently to the tunneling process, enabling the TMR ratio to reach about 103% while managing structural complexity through systematic design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different segments of the barrier are assigned different local properties (materials, thicknesses, potential heights) optimized for specific functions. For example, certain segments have higher potentials to block electrons while others have lower potentials to allow tunneling, creating local quality variations that enhance overall TMR ratio to 107%.

Inventive Principle:

Principle #3Local quality

3Temperature

If conventional magnetic tunnel junctions are used, then the device can operate at room temperature, but the sensitivity is insufficient compared to superconducting quantum interference devices

Engineering Contradiction:

Improveoperating temperatureVSAvoidsensitivity

Core Design Contradiction:

TemperatureVSMeasurement precision

Solution Approach 1:

The patent optimizes critical parameters including barrier thickness (3-5 nm), material composition ratios, and potential height differences to maximize TMR ratio. By achieving TMR ratio of 107% through parameter optimization, the device attains sensitivity comparable to SQUID devices while maintaining room temperature operation capability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite barrier structures combining different insulating materials (such as Al2O3, MgO, Ta2O5) with varying thicknesses and potential heights. This composite approach leverages the advantageous properties of each material to achieve enhanced TMR ratio of 107% through constructive interference of tunneling electrons.

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

The graphene-based magnetic tunnel junction with segmented potentials significantly enhances the TMR ratio, improving the sensitivity and performance of hard disk read heads and magnetic field sensors, enabling them to operate effectively at room temperature with increased sensitivity comparable to superconducting quantum interference devices.

Implementation Method 1

The barrier segment of a magnetic tunnel junction must be thin enough to allow the tunnel effect in quantum mechanics

Methodology Applied

Scientific EffectQuantum tunneling:

Implementation Method 2

Graphene nanoribbons (GNRs) with designed edges offer methods to manipulate spin-polarized electrons

Methodology Applied

Scientific EffectSpin transport:

Data Source

PatentUS9537089B2Method and device for huge magnetoresistance in graphene-based magnetic tunnel junctions with segmented potentials

Publication Date: 2017.01.03 NAT TAIWAN UNIV

AI summary

A graphene-based magnetic tunnel junction is disclosed. The magnetic tunnel junction can enhance the tunnel magnetoresistance ratio and a device including the magnetic tunnel junction. The magnetic tunnel junction includes: a pinned layer; a free layer; and a graphene with segmented potentials configured between the pinned layer and the free layer. The magnetic tunnel junction may be a series or parallel connection of the above-mentioned basic form. The device including a magnetic tunnel junction may be a magnetic random access memory bit cell, a magnetic tunnel junction transistor device, a magnetic field sensor, etc.