Spin-Orbit Torque Magnetization Element with Tuned Spin Hall Angle

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Solution Overview

Problem

Current magnetoresistance effect elements require high reversal current density for magnetization reversal, which can lead to damage and reduced lifespan, and there is a need to reduce this density for improved efficiency and longevity.

Innovation Solution

A spin current magnetization rotational element is designed with a spin-orbit torque wiring and ferromagnetic layers, where the polarity of the spin Hall angle is controlled in inserted layers to generate a larger spin-orbit torque, reducing the reversal current density by optimizing the spin Hall effect and ferromagnetic layer configurations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If magnetization reversal is performed using spin transfer torque (STT) in conventional TMR elements, then magnetization reversal can be achieved, but the reversal current density is high which reduces element lifespan

Engineering Contradiction:

Improveelement lifespanVSAvoidreversal current density

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the conventional STT mechanism (where current flows directly through the magnetoresistance effect element causing mechanical stress and damage) with a SOT mechanism using spin Hall effect. A spin-orbit torque wiring layer is introduced that generates spin current through the spin Hall effect when current flows through it, and this spin current acts on the ferromagnetic layer to induce magnetization reversal without the need for high current density through the element itself, thus substituting the direct electrical-mechanical interaction with a spin-mediated interaction that preserves element integrity and extends lifespan

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If magnetization reversal is performed using spin-orbit torque (SOT) with spin Hall effect, then element lifespan is extended by avoiding current flow through the magnetoresistance effect element, but the reversal current density remains comparable to STT methods

Engineering Contradiction:

Improveelement lifespanVSAvoidreversal current density

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent optimizes the spin Hall angle parameter by carefully selecting the material composition of the spin-orbit torque wiring layer. By choosing materials with specific spin Hall angles (such as Cu with specific thickness ranges, or alloys like CoFeB), the spin current generation efficiency is maximized. This parameter optimization allows the spin-orbit torque to achieve magnetization reversal at lower current densities compared to conventional SOT implementations, while maintaining the reliability benefits of avoiding direct current flow through the magnetoresistance effect element

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures in the spin-orbit torque wiring layer, combining different materials with complementary properties. For example, it uses combinations such as Cu/CoFeB/Cu or Cu/CoFe/Cu multilayer structures where each material contributes specific properties: Cu provides high spin Hall angle and good electrical conductivity, while CoFeB or CoFe provides ferromagnetic properties and interface engineering capabilities. This composite approach enhances the overall spin current generation efficiency and reduces the reversal current density

Inventive Principle:

Principle #40Composite materials

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 efficient magnetization reversal with reduced reversal current density, enhancing the lifespan and drive efficiency of magnetoresistance effect elements.

Implementation Method 1

the magnetization of the functional magnetic coupling layer is reversed by utilizing the SOT due to the spin injected by the spin Hall effect

Methodology Applied

Scientific EffectSpin Hall Effect: Hall Effect

Implementation Method 2

magnetization reversal utilizing a pure spin current generated by spin-orbit interaction, which performs magnetization reversal by a mechanism different from that of STT

Methodology Applied

Scientific EffectSpin-Orbit Interaction:

Implementation Method 3

the pure spin current generated by the spin-orbit interaction or the Rashba effect at the interface of dissimilar materials induces the spin-orbit torque (SOT), and magnetization reversal occurs due to SOT

Methodology Applied

Scientific EffectSpin-Orbit Torque:

Implementation Method 4

the pure spin current generated by the spin-orbit interaction or the Rashba effect at the interface of dissimilar materials induces the spin-orbit torque (SOT)

Methodology Applied

Scientific EffectRashba Effect:

Data Source

PatentUS11222919B2Spin current magnetization rotational element, spin-orbit torque magnetoresistance effect element, and magnetic memory

Publication Date: 2022.01.11 TDK CORP

AI summary

A spin current magnetization rotational element includes: a spin-orbit torque wiring extending in a first direction; and a first ferromagnetic layer laminated in a second direction intersecting with the spin-orbit torque wiring, wherein the first ferromagnetic layer comprises a plurality of ferromagnetic constituent layers and at least one inserted layer sandwiched between adjacent ferromagnetic constituent layers, and polarities of spin Hall angles of two layers, which sandwich at least one of the ferromagnetic constituent layers among the plurality of the ferromagnetic constituent layers, differ.