Magnetic Storage Element with Heat Generator for Low-Current Spin Injection

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Solution Overview

Problem

Magnetic memory utilizing spin injection magnetization reversal faces challenges in reducing the current necessary for magnetization reversal without compromising information retention characteristics, especially as element size decreases, leading to increased power consumption and difficulty in enhancing recording density.

Innovation Solution

Incorporating a heat generator to heat the recording layer and using a magnetic material with specific temperature-dependent magnetization characteristics, where magnetization at 150° C. is at least 50% of room temperature magnetization and decreases to 10-80% between 150° C. to 200° C., to reduce the current required for spin injection magnetization reversal while maintaining stable information retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the film thickness of the recording layer is increased to avoid thermal fluctuation and improve information retention, then information retention characteristic is improved, but the current necessary for spin injection magnetization reversal increases leading to increased power consumption

Engineering Contradiction:

Improveinformation retention characteristicVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies parameter changes by utilizing temperature as a control parameter. The recording layer's magnetization is temporarily reduced through heating during the write operation, which lowers the current threshold for spin injection magnetization reversal. After writing, the layer cools down and returns to its original high-magnetization state, ensuring stable information retention. This dynamic parameter change allows thin film design with low power consumption while maintaining reliability.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the element size is reduced to enhance recording density, then recording density is improved, but the recording retention capability deteriorates due to thermal fluctuation

Engineering Contradiction:

Improverecording densityVSAvoidrecording retention capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent uses parameter changes by dynamically controlling the temperature of the recording layer during write operations. Heating temporarily reduces the magnetization and lowers the thermal stability parameter, making it easier to switch magnetization states with lower current in smaller elements. After cooling, the element regains its thermal stability, preventing thermal fluctuation issues even in reduced-size elements, thus enabling high recording density without sacrificing retention capability.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If the current necessary for magnetization reversal is reduced to lower power consumption, then power consumption is reduced, but the ability to maintain stable magnetization against thermal fluctuation deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidmagnetization stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies periodic action through transient heating during write operations. The recording layer is periodically heated to a temperature where magnetization is reduced, allowing low-current writing. Between heating pulses, the layer remains in its stable, high-magnetization state. This periodic temperature modulation enables low-power operation during writing while maintaining magnetization stability during data retention, resolving the contradiction between power consumption and reliability.

Inventive Principle:

Principle #19Periodic action

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 allows for information rewriting with a small current while maintaining stability against thermal fluctuations, effectively reducing the spin injection magnetization reversal current without lowering information retention characteristics.

Implementation Method 1

a heat generator configured to heat the recording layer

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

recording information changes due to thermal fluctuation

Methodology Applied

Scientific EffectThermal fluctuation:

Implementation Method 3

magnetization at 150° C. is at least 50% of magnetization at a room temperature and magnetization at a temperature in the range from 150° C. to 200° C. is in the range from 10% to 80% of magnetization at a room temperature

Methodology Applied

Scientific EffectTemperature-dependent magnetization:

Implementation Method 4

spin injection magnetization reversal method of causing magnetization reversal by injecting spin-polarized electrons directly into the recording layer

Methodology Applied

Scientific EffectSpin injection:

Data Source

PatentUS9196824B2Magnetic storage element and magnetic memory

Publication Date: 2015.11.24 SONY GROUP CORP

AI summary

A magnetic storage element including a recording layer and a heat generator. The recording layer has a magnetization direction that is configured to change via spin injection so that information can be recorded. The heat generator is positioned to heat the recording layer. The recording layer comprises (i) cobalt and iron and (ii) a non-magnetic element or a non-magnetic element and an oxide.