Spin Valve Layer Stack for Non-Collinear Magnetization States

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Solution Overview

Problem

Classical spin valve devices are limited to switching between only two collinear states, restricting their applications due to the need for a digital device with limited scope.

Innovation Solution

A method involving a layer stack with a substrate, a first ferromagnetic layer with uniaxial magnetic anisotropy, a non-magnetic layer, a second ferromagnetic layer with unidirectional anisotropy, and an antiferromagnetic layer, where the stack is heated above the antiferromagnetic's Néel temperature, subjected to a magnetic field at an arbitrary angle, and then cooled to fix a non-collinear magnetization state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a classical spin valve device uses collinear magnetization states for switching, then the device structure is simple and easy to manufacture, but the application scope is limited due to only two states being available

Engineering Contradiction:

Improveapplication scopeVSAvoiddevice structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the magnetization configuration parameter from collinear (parallel/antiparallel) to non-collinear arrangements. By introducing a uniaxial magnetic anisotropy in the first ferromagnetic layer and using exchange coupling through the non-magnetic layer, the system achieves multiple stable magnetization states with different angles, thereby expanding application scope to multi-state memory and neuromorphic computing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite layered structure consisting of multiple ferromagnetic layers with different anisotropy characteristics separated by a non-magnetic layer. This composite structure enables independent control of magnetization directions in each layer through exchange coupling and anisotropy engineering, achieving multiple stable states while maintaining a relatively simple layered architecture

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If a spin valve device is designed with non-collinear magnetization states, then multi-state functionality is achieved, but the fabrication process becomes more complex

Engineering Contradiction:

Improvemulti-state capabilityVSAvoidfabrication process

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent introduces uniaxial magnetic anisotropy in the first ferromagnetic layer during the fabrication process itself, rather than requiring post-fabrication manipulation. This preliminary establishment of anisotropy axes enables subsequent magnetic field application to reliably set specific non-collinear magnetization angles, simplifying the overall fabrication process while achieving multi-state functionality

Inventive Principle:

Principle #10Preliminary 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 method allows for a non-volatile magnetic state with a well-defined non-collinear angle between magnetization vectors, expanding the device's capabilities and enabling multi-state memory cells and artificial neuron networks.

Implementation Method 1

heating the layer stack above the Néel temperature TN of the antiferromagnetic layer

Methodology Applied

Scientific EffectNéel temperature phase transition: Néel Temperature

Implementation Method 2

The magnetization M2 is pinned by a strong exchange bias (EB) field to an antiferromagnet

Methodology Applied

Scientific EffectExchange bias:

Data Source

PatentUS20240415023A1A method for fabricating a magnetic spin valve device comprising ferromagnetic layers with non-collinear magnetizations

Publication Date: 2024.12.12 MAX PLANCK GESELLSCHAFT ZUR FOERDERUNG DER WISSENSCHAFTEN EV

AI summary

A method for fabricating a magnetic device comprises providing a layer stack, the layer stack comprising a substrate, a first ferromagnetic layer disposed above the substrate, the first ferromagnetic layer comprising a uniaxial magnetic anisotropy including an easy axis, a non-magnetic layer disposed on the first ferromagnetic layer, a second ferromagnetic layer disposed on the non-magnetic layer, the second ferromagnetic layer comprising a unidirectional anisotropy, and an antiferromagnetic layer disposed on the second ferromagnetic layer, the antiferromagnetic layer comprising a Néel temperature TN; heating the layer stack above the Néel temperature TN of the antiferromagnetic layer; applying a magnetic field HCL to the layer stack, the magnetic field HCL comprising a magnetic field direction having an arbitrary angle with respect to the easy axis; cooling the layer stack below the Néel temperature TN of the antiferromagnetic layer with the magnetic field HCL applied; and removing the magnetic field HCL.