Composite Free Layer for Field-Free Spin Orbit Torque Switching

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Solution Overview

Problem

Conventional semiconductor devices face limitations in scaling due to device reliability and increased power consumption, and existing spintronic devices require high critical current densities for magnetization switching, which impedes energy-efficient applications and induces stress on tunnel barrier layers.

Innovation Solution

The development of a composite free layer with a magnetic easy axis oriented out of the plane, comprising a Co-based alloy, Fe-based alloy, or Heusler alloy sub-layers with an intermediate rare earth element layer, enabling field-free spin orbit torque (SOT) induced magnetization switching with lower critical current densities and improved thermal stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional semiconductor devices are scaled down to improve device density, then productivity increases, but device reliability deteriorates and power consumption increases

Engineering Contradiction:

Improvedevice densityVSAvoiddevice reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent replaces conventional charge-based electronic devices with spin-based spintronic devices that utilize the intrinsic spin of electrons and magnetic moments. This substitution enables new mechanisms for data storage and processing that are less susceptible to scaling limitations and provide improved reliability through magnetic state retention without power.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention employs composite magnetic layer structures including CoFeB/magnetite/CoFeB trilayers with perpendicular magnetic anisotropy. These composite materials provide enhanced thermal stability, controlled magnetization switching, and improved device reliability while maintaining scalability.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If existing spintronic devices use high critical current densities for magnetization switching, then magnetization switching is achieved, but energy consumption increases and stress is induced on tunnel barrier layers

Engineering Contradiction:

Improvemagnetization switchingVSAvoidenergy consumption

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent introduces perpendicular magnetic anisotropy (PMA) in the free layer, which fundamentally changes the magnetization switching mechanism from in-plane to out-of-plane switching. This parameter change enables field-free switching and reduces the critical current density by utilizing spin-orbit coupling effects more efficiently, thereby lowering energy consumption.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite layer structure with CoFeB/magnetite/CoFeB trilayers where each layer has specific local properties. The magnetite layer provides Dzyaloshinskii-Moriya interaction (DMI) for field-free switching, while the CoFeB layers provide high spin polarization and perpendicular anisotropy. This local differentiation of material properties enables efficient low-energy switching.

Inventive Principle:

Principle #3Local quality

3Ease of operation

If existing spintronic devices use high critical current densities, then magnetization switching is achieved, but stress is induced on tunnel barrier layers reducing reliability

Engineering Contradiction:

Improvemagnetization switchingVSAvoidtunnel barrier layer stress

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

By implementing perpendicular magnetic anisotropy and utilizing spin-orbit coupling in the composite free layer structure, the patent reduces the critical current density for magnetization switching. This parameter change decreases the stress applied to the MgO tunnel barrier layer, preventing structural degradation and maintaining high device reliability over extended operational cycles.

Inventive Principle:

Principle #35Parameter changes

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 solution allows for energy-efficient and high-performance spintronic devices with reduced critical current densities and enhanced thermal stability, enabling more efficient magnetization switching and increased operational cycles without stressing tunnel barrier layers.

Implementation Method 1

enabling field-free spin orbit torque (SOT) induced magnetization switching

Methodology Applied

Scientific EffectSpin orbit torque:

Implementation Method 2

The composite free layer exhibits a magnetic easy axis oriented out of a plane of the composite free layer

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Data Source

PatentUS10354709B2Composite free magnetic layers

Publication Date: 2019.07.16 REGENTS OF THE UNIVERSITY OF MINNESOTA

AI summary

A magnetic device may include a composite free layer that includes a first sub-layer comprising at least one of a Co-based alloy, a Fe-based alloy, or a Heusler alloy; a second sub-layer comprising at least one of a Co-based alloy, a Fe-based alloy, or a Heusler alloy; and an intermediate sub-layer between the first sub-layer and the second sub-layer. The composite free layer exhibits a magnetic easy axis oriented out of a plane of the composite free layer.