Magnetic Storage Device With Composite Ferromagnetic Layers

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Solution Overview

Problem

Magnetic storage devices, such as MRAM, face challenges in achieving improved resistance change rate and retention properties due to limitations in the magnetoresistive effect element's design, particularly in maintaining exchange-coupling and perpendicular magnetic anisotropy while preventing crystallization and loss of soft magnetism.

Innovation Solution

The magnetic storage device incorporates a magnetoresistive effect element with a stacked body structure including a ferromagnetic material with a bcc crystal structure, a soft magnetic material with an amorphous structure and additives like carbides or borides, and a ferromagnetic material with an fcc structure, which maintains exchange-coupling and enhances perpendicular magnetic anisotropy, allowing for improved resistance change ratio and retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a magnetoresistive effect element uses a stacked body with ferromagnetic layers to maintain exchange-coupling and perpendicular magnetic anisotropy, then resistance change ratio and retention are improved, but the device complexity increases due to multiple layered structures

Engineering Contradiction:

Improveretention propertyVSAvoidstacked body structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The storage layer is segmented into multiple ferromagnetic layers (first ferromagnetic layer and second ferromagnetic layer) with different crystal structures (bcc and fcc respectively), separated by a soft magnetic material layer. This segmentation allows each layer to contribute different magnetic properties, achieving both exchange-coupling and perpendicular magnetic anisotropy while maintaining manageable structural complexity through functional division

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stacked body employs composite material structure combining ferromagnetic materials with bcc and fcc crystal structures, interspersed with soft magnetic materials containing carbide or boride additives. This composite approach enables simultaneous achievement of exchange-coupling between layers and perpendicular magnetic anisotropy within the structure, improving retention without excessive complexity increase

Inventive Principle:

Principle #40Composite materials

2Reliability

If the soft magnetic material contains additives like carbides or borides to prevent crystallization, then retention and resistance change ratio are improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveretention propertyVSAvoidamorphous structure maintenance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The soft magnetic material's composition is modified by adding specific compounds (carbides or borides) that alter its crystallization behavior. This parameter change in material composition enables the material to maintain amorphous structure under processing conditions, preventing unwanted crystallization while achieving improved retention and resistance change ratio with manageable manufacturing precision

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The soft magnetic material with carbide or boride additives serves as a sacrificial functional layer that maintains amorphous structure during device fabrication and operation. The additives prevent crystallization during manufacturing processes, ensuring the layer remains effective for exchange-coupling without requiring extremely precise manufacturing control

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 enhances the magnetization retention and resistance change ratio of the magnetoresistive effect element, improving the overall performance and stability against external disturbances like heat and magnetic fields.

Implementation Method 1

A magnetic storage device, such as magnetoresistive random access memory (MRAM), using a magnetoresistive effect element as a storage element is known

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Implementation Method 2

a second ferromagnetic layer exchange-coupled with the first ferromagnetic layer

Methodology Applied

Scientific EffectExchange-coupling:

Implementation Method 3

enhances perpendicular magnetic anisotropy

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Data Source

PatentUS10978636B2Magnetic storage device

Publication Date: 2021.04.13 KIOXIA CORP

AI summary

According to one embodiment, a storage device includes a magnetoresistive effect element comprising a nonmagnetic layer and a stacked body on the nonmagnetic layer. The stacked body includes a first ferromagnetic layer on the nonmagnetic layer, a second ferromagnetic layer exchange-coupled with the first ferromagnetic layer, and a magnetic layer between the first ferromagnetic layer and the second ferromagnetic layer. The magnetic layer includes a magnetic material and at least one compound selected from among a carbide, a nitride, and a boride.