Magnetic Memory Devices Using Domain Wall Motion for Storage

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Solution Overview

Problem

Conventional non-volatile information storage devices, such as HDDs and flash memory, face issues like mechanical failure, low reading and writing speeds, short lifetimes, and high manufacturing costs, while magnetic domain wall movement-based storage devices struggle with precise control of magnetic domains and domain walls.

Innovation Solution

A magnetic memory device with a multi-layer cross-point array structure, featuring free layers, reference layers with magnetic domains and domain walls, and switching elements, allowing for easy read/write operations through controlled magnetic domain wall movement and spin transfer torque, eliminating the need for rotating mechanical devices and anti-ferromagnetic layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If magnetic domain wall movement is used for information storage, then storage capacity can be increased without rotating mechanical devices, but precise control of magnetic domains and domain walls becomes difficult

Engineering Contradiction:

Improvestorage capacityVSAvoidcontrol precision

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The patent applies local quality by creating distinct magnetic domains with different magnetization directions (up or down) in specific regions of the magnetic track. Each domain serves as a localized information storage unit, allowing precise control through localized magnetic field application or current injection. The domain walls are positioned at specific locations to define domain boundaries, enabling independent control of each domain's magnetization state without affecting adjacent domains.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes parameter changes by varying the magnetization direction (up or down) of magnetic domains to represent binary information. The magnetization state of each domain can be switched by changing the direction or magnitude of applied current or magnetic field, providing a reliable and controllable mechanism for writing and reading information while maintaining precise domain control.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional non-volatile RAM (flash memory) is used, then no rotating mechanical devices are needed, but reading and writing speeds become relatively low

Engineering Contradiction:

Improvemechanical reliabilityVSAvoidreading and writing speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent replaces the mechanical rotating disk system of HDDs with a static magnetic track structure where information is stored in magnetic domains. This eliminates mechanical moving parts while maintaining high-speed access through electrical or magnetic control of domain magnetization, achieving both mechanical reliability and fast read/write operations characteristic of solid-state memory.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Quantity of substance

If HDD structure with rotating mechanical device is used, then large storage capacity can be achieved, but mechanical wear reduces reliability

Engineering Contradiction:

Improvestorage capacityVSAvoidoperational reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent eliminates the rotating mechanical disk and read/write head assembly by using a static magnetic track with controllable magnetic domains. Information storage is achieved through magnetic domain orientation rather than physical media rotation, removing mechanical wear components entirely while maintaining large storage capacity through dense domain packing and multi-layer magnetic track structures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution provides a high-degree of integration, simplified device structure, improved thermal stability, and easier control of magnetic domains, enabling efficient information storage with higher storage capacity and reduced operational complexity.

Implementation Method 1

supplying a write current between the first free layer and the first reference layer. Information to be written to the first free layer by the write current is determined according to which of the at least two magnetic domains of the first reference layer corresponds to the first free layer

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS8681542B2Magnetic memory devices and methods of operating the same

Publication Date: 2014.03.25 SAMSUNG ELECTRONICS CO LTD

AI summary

A magnetic memory device includes: a free layer for storing information; and a reference layer disposed on a first surface of the free layer. The reference layer includes at least two magnetic domains and a magnetic domain wall between the at least two magnetic domains. The reference layer extends past both ends of the free layer. The magnetic memory device further includes a switching element connected to a second surface of the free layer. Another magnetic memory device includes: a first reference layer having a first magnetic domain wall; a second reference layer having a second magnetic domain wall; and a memory structure between the first and second reference layers. The memory structure includes: a first free layer adjacent to the first reference layer; a second free layer adjacent to the second reference layer; and a switching element between the first and second free layers.