Magnetic Tunnel Junction Free Layer Pinning for Stable Domain Walls

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Solution Overview

Problem

Existing magnetic memory devices require complex structures and large magnetic field generation layers to form domain walls, complicating the device design and hindering size reduction.

Innovation Solution

Incorporating a domain wall pinning site in the free layer with features such as notches or doping areas to stabilize the pinned domain wall, eliminating the need for a magnetic field generation layer and simplifying the structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a magnetic field generation layer is used to form domain walls, then domain wall formation is achieved, but device structure becomes complex and size increases

Engineering Contradiction:

Improvedomain wall formationVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the magnetic field generation layer from the device structure. Instead of using a separate layer to generate magnetic fields for domain wall formation, the invention uses the spin orbit torque layer to directly induce domain wall formation through spin current, removing the unnecessary component and simplifying the overall structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the magnetic field-based domain wall formation mechanism with a spin current-based mechanism. The spin orbit torque layer generates spin current that directly manipulates magnetization in the free layer to form domain walls, substituting the traditional magnetic field generation approach with a more efficient spin transport mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a magnetic field generation layer is used to form domain walls, then domain wall formation is achieved, but manufacturing cost increases

Engineering Contradiction:

Improvedomain wall formationVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

By removing the magnetic field generation layer, the patent reduces the number of manufacturing steps and materials required. The spin orbit torque layer serves dual purposes: generating spin current for domain wall formation and providing torque for magnetization switching, eliminating the need for separate magnetic field generation structures and associated fabrication processes.

Inventive Principle:

Principle #2Taking out (Extraction)

3Device complexity

If the pinned domain wall is not fixed, then device structure is simpler, but write operation stability decreases

Engineering Contradiction:

Improvestructure simplicityVSAvoidwrite operation stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies local quality by creating a specific pinning site region in the free layer with different properties from the rest of the layer. This localized region has enhanced magnetization stability or structural features that preferentially pin the pinned domain wall, allowing the rest of the device to maintain simplicity while achieving the required operational stability locally.

Inventive Principle:

Principle #3Local quality

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 approach allows for a simpler, smaller magnetic memory device design with reduced manufacturing costs and improved write operation stability by fixing the pinned domain wall, thereby enhancing the device's operational efficiency and reducing errors.

Implementation Method 1

a spin orbit torque layer arranged at an opposite side of the tunnel barrier layer with respect to the free layer and configured to change the magnetization direction of the free layer

Methodology Applied

Scientific EffectSpin-orbit torque:

Implementation Method 2

The resistance of a magnetic tunnel junction element varies depending on the magnetization direction of a free layer. For example, when the magnetization direction of a free layer is the same as the magnetization direction of a pinned layer, a magnetic tunnel junction element may have a low resistance value

Methodology Applied

Scientific EffectMagnetic tunneling: Magnetoresistance

Implementation Method 3

A domain wall exists between two magnetic domains with different magnetization directions in a free layer, and when current flows in the free layer, the magnetization directions of two magnetic domains vary, and the domain wall moves accordingly

Methodology Applied

Scientific EffectDomain wall motion:

Data Source

PatentUS20260020248A1Magnetic memory device including magnetic domain wall pinning site and memory apparatus including the same

Publication Date: 2026.01.15 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic memory device includes a magnetic tunneling junction including a free layer, a tunnel barrier layer, and a pinned layer, a spin orbit torque layer at an opposite side of the tunnel barrier layer with respect to the free layer to change a magnetization direction of the free layer, and a domain wall pinning site configured to fix the pinned domain wall. The free layer includes a first region having a first width and in which a movable domain wall moves, and second and third regions extending from both end portions of the first region and respectively having a second width and a third width, which are greater than the first width. A domain wall pinning site is in the third region of the free layer and fix a pinned domain wall among the movable domain wall and the pinned domain wall, which are formed in an initialization process.