Spin-Orbit Torque Magnetization Control via Ferromagnetic Electrode

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Solution Overview

Problem

Magnetization reversal in magneto resistance effect elements using spin transfer torque requires high current density, leading to energy inefficiency and potential instability due to heat generation, while pure spin current methods necessitate high perpendicular current densities to inject sufficient magnetization, compromising element lifespan.

Innovation Solution

A spin current magnetization rotational element is designed with a ferromagnetic electrode layer near a ferromagnetic metal layer, utilizing spin polarization current and spin-orbit torque to change magnetization direction, allowing for magnetization reversal with a low current by diffusing spin from the electrode layer and generating spin-orbit torque, thus reducing the need for high current densities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spin transfer torque (STT) is used for magnetization reversal, then magnetization reversal can be achieved, but high current density is required leading to energy inefficiency and heat generation

Engineering Contradiction:

Improvemagnetization reversal capabilityVSAvoidcurrent density

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The invention segments the current path from the magnetization reversal path by introducing a separate spin injection layer. The current flows through the spin injection layer to generate spin current, which then acts on the ferromagnetic layer without the need for high direct current density through the magneto resistance element, thus reducing energy consumption while maintaining reversal capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spin injection layer acts as an intermediary that converts charge current into spin current via the spin Hall effect. This intermediary mechanism allows magnetization reversal to be achieved through spin-orbit torque rather than direct spin transfer torque, reducing the required current density and improving energy efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

2Duration of action of stationary object

If pure spin current is generated by spin-orbit interaction to reduce reversal current, then current through magneto resistance element is zero extending lifespan, but high perpendicular current density is required generating heat

Engineering Contradiction:

Improveelement lifespanVSAvoidheat generation

Core Design Contradiction:

Duration of action of stationary objectVSTemperature

Solution Approach 1:

The invention applies local quality by creating a specific geometric configuration where the spin injection layer is positioned adjacent to and overlapping with the ferromagnetic layer in a top view. This localized arrangement ensures that spin current is generated precisely where needed, improving the efficiency of spin-orbit torque generation and reducing the overall current density required, thereby reducing heat generation while extending element lifespan

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

Enables magnetization direction change with a low current, enhancing energy efficiency and extending the lifespan of magneto resistance effect elements by leveraging spin diffusion and spin-orbit torque without the heat-related instability issues.

Implementation Method 1

a direction of magnetization of the ferromagnetic metal layer is variable by spin-orbit torque generated by a spin-orbit interaction in the spin-orbit torque wiring

Methodology Applied

Scientific EffectSpin-orbit interaction:

Implementation Method 2

an influence of spin diffused from the ferromagnetic electrode layer

Methodology Applied

Scientific EffectSpin diffusion: Diffusion

Data Source

PatentUS10454023B2Spin current magnetization rotational element

Publication Date: 2019.10.22 TDK CORP

AI summary

A spin current magnetization rotational element includes: a ferromagnetic metal layer; a spin-orbit torque wiring configured to extend in a first direction perpendicular to a lamination direction of the ferromagnetic metal layer and formed on one surface of the ferromagnetic metal layer; and a ferromagnetic electrode layer formed outside the ferromagnetic metal layer on any of surfaces of the spin-orbit torque wiring in a top view from the lamination direction. A direction of magnetization of the ferromagnetic metal layer is changeable by spin-orbit torque generated by a spin-orbit interaction in the spin-orbit torque wiring and an influence of spin diffused from the ferromagnetic electrode layer.