Magnetic Storage Device Stacked Structure for Data Retention

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Solution Overview

Problem

Magnetic storage devices face challenges in maintaining data retention and resistance switching stability due to external disturbances like heat and magnetic fields, particularly in high-temperature environments, and require efficient spin torque injection with minimal write current.

Innovation Solution

A magnetic storage device with a stacked structure comprising a ferromagnetic layer, an anti-ferromagnet, and a soft or hard magnetic layer, where the anti-ferromagnet is exchange-coupled with the ferromagnetic layer, enhancing magnetization stability and retention while allowing efficient spin torque injection with reduced write current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional magnetoresistive effect element is used, then the device structure is simple, but data retention and resistance switching stability deteriorate under external disturbances like heat and magnetic fields

Engineering Contradiction:

Improvedata retention and resistance switching stabilityVSAvoidstacked structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The storage layer is segmented into multiple functional sub-layers: a ferromagnetic layer for stable magnetization, a soft magnetic layer for spin torque injection, and a hard magnetic layer for magnetic field stabilization. This segmentation allows each layer to perform its specific function optimally, improving overall reliability while managing complexity through functional decomposition

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a composite stacked structure combining different magnetic materials (ferromagnet, soft magnet, hard magnet) with distinct magnetic properties. This composite approach enables the system to achieve both stability and responsiveness by leveraging the complementary characteristics of each material layer

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If high write current is used for spin torque injection, then magnetization reversal is achieved, but energy consumption increases

Engineering Contradiction:

Improvewrite current efficiencyVSAvoidmagnetization reversal stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent optimizes the magnetic parameters of each layer, particularly the magnetization strength and anisotropy, to achieve efficient spin torque injection. By carefully controlling the magnetic field parameters and layer thicknesses, the system achieves magnetization reversal at lower current densities while maintaining stability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The soft magnetic layer acts as an intermediary between the current source and the ferromagnetic storage layer. This intermediary layer efficiently transmits spin torque from the current to the storage layer, improving the coupling efficiency and reducing the overall energy required for magnetization reversal

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If the anti-ferromagnet exchange coupling is strong, then magnetization stability improves, but the device becomes more sensitive to external disturbances

Engineering Contradiction:

Improvemagnetization stabilityVSAvoidsensitivity to external disturbances

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent applies different magnetic coupling strengths at different locations within the stacked structure. The anti-ferromagnetic exchange coupling is optimized locally at the interface between specific layers to provide stability where needed, while other regions maintain flexibility to resist external disturbances. This local optimization allows simultaneous achievement of stability and disturbance resistance

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

The solution improves data retention and resistance switching stability by maintaining exchange coupling even at high temperatures, suppressing spin torque scattering, and allowing efficient magnetization reversal with lower write current, thus enhancing the device's performance and reliability.

Implementation Method 1

an anti-ferromagnet being exchange-coupled with the first ferromagnet

Methodology Applied

Scientific EffectExchange coupling: Magnetism

Implementation Method 2

A magnetic storage device (MRAM: Magnetoresistive Random Access Memory) that uses a magnetoresistive effect element as a storage element

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Implementation Method 3

allowing efficient spin torque injection with reduced write current

Methodology Applied

Scientific EffectSpin torque:

Data Source

PatentUS11133456B2Magnetic storage device

Publication Date: 2021.09.28 KIOXIA CORP

AI summary

According to one embodiment, a magnetic storage device includes: a magnetoresistive effect element including a non-magnet, and a stacked structure on the non-magnet, the stacked structure including: a first ferromagnet on the non-magnet; an anti-ferromagnet being exchange-coupled with the first ferromagnet; and a second ferromagnet between the first ferromagnet and the anti-ferromagnet. The stacked structure is configured to: have a first resistance value in response to a first current flowing through the stacked structure in a first direction, and have a second resistance value different from the first resistance value in response to a second current flowing through the stacked structure in a second direction opposite to the first direction.