Antiparallel Layer Structures for Magnetoresistive Sensor Pinning
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Solution Overview
Problem
Magnetoresistive magnetic field sensors with single ferromagnetic reference layers exhibit low thermal stability and require high magnetic flux densities for pinning, making it difficult to produce multiple layer stacks with different magnetic orientations, and conventional pinning methods are inefficient and limited by the need for strong magnetic fields.
Innovation Solution
An arrangement of adjacent layer structures with an antiferromagnetic layer, a first ferromagnetic layer, and a second ferromagnetic layer antiparallel coupled via a non-magnetic layer, allowing for pinning at low magnetic field strengths and enabling different pinning directions for closely adjacent layer structures, using a soft-magnetic structuring element to guide the pretreatment magnetic field and create a pinning field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single ferromagnetic reference layer is used, then the device complexity is reduced, but thermal stability deteriorates and high magnetic flux densities are required for pinning
Solution Approach 1:
The reference layer is segmented into two separate ferromagnetic layers (first and second ferromagnetic layers) with different magnetic moments, where the first layer has higher magnetic moment and the second layer has lower magnetic moment. These layers are coupled antiparallel to each other, creating a more stable reference layer structure that can better withstand thermal fluctuations while requiring lower pinning field strengths.
Solution Approach 2:
The reference layer is constructed as a composite structure combining two ferromagnetic layers with different magnetic properties, coupled through a non-magnetic coupling layer. This composite structure leverages the different magnetic moments of the two layers to achieve both thermal stability and reduced pinning field requirements.
2Reliability
If high magnetic flux densities are used for pinning, then pinning effectiveness is improved, but the ability to produce multiple layer stacks with different magnetic orientations deteriorates
Solution Approach 1:
A soft-magnetic structuring element is introduced to create locally differentiated magnetic environments. This structuring element guides the pretreatment magnetic field to generate different pinning field directions at different locations, enabling adjacent layer stacks to be pinned in different directions (e.g., first direction and second direction) without requiring high magnetic flux densities.
Solution Approach 2:
A soft-magnetic structuring element is introduced as an intermediary component between the magnetic field source and the layer stacks. This structuring element mediates the magnetic field distribution, converting a uniform pretreatment magnetic field into differentiated pinning fields that enable diverse magnetic orientations in adjacent layer stacks.
3Reliability
If strongly coupled antiparallel ferromagnetic layers are used, then thermal stability is improved, but the pinning field strength requirement increases
Solution Approach 1:
The magnetic moments of the two ferromagnetic layers are deliberately made different (first layer has higher magnetic moment, second layer has lower magnetic moment), creating an unbalanced antiparallel coupled structure. This parameter change optimizes the balance between thermal stability and pinning field strength, achieving thermal stability without requiring excessively high pinning fields.
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 significantly reduces the required pinning field strength by a factor of 10, enhances thermal and magnetic stability, and allows for the production of multiple layer stacks with diverse pinning directions, improving the feasibility and precision of magnetic field sensor construction.
Implementation Method 1
an exchange coupling exists between the antiferromagnetic layer and the first ferromagnetic layer
Implementation Method 2
the second ferromagnetic layer is coupled antiparallel to the first ferromagnetic layer via a non-magnetic coupling layer arranged between the first and the second ferromagnetic layer
Implementation Method 3
using a soft-magnetic structuring element to guide the pretreatment magnetic field and create a pinning field
Implementation Method 4
Magnetoresistive magnetic field sensors are based on the giant magnetoresistance effect (GMR effect) or the tunnel magnetoresistance effect (TMR effect)
Implementation Method 5
Magnetoresistive magnetic field sensors are based on the giant magnetoresistance effect (GMR effect) or the tunnel magnetoresistance effect (TMR effect)
Data Source
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AI summary
The present invention relates to an arrangement of at least two adjacently arranged layer structures for a magnetoresistive magnetic field sensor. In this case, each layer structure comprises at least one antiferromagnetic layer, and a first ferromagnetic layer having a first magnetic moment. There is exchange coupling between the antiferromagnetic layer and the first ferromagnetic layer. Moreover, said structure comprises a second ferromagnetic layer having a second magnetic moment, wherein the second ferromagnetic layer is coupled in antiparallel with the first ferromagnetic layer via a non-magnetic coupling layer arranged between the first and the second ferromagnetic layer. It is proposed that the magnetizations of the corresponding first and corresponding second ferromagnetic layers of the adjacently arranged layer structures deviate from one another, in particular are oriented substantially oppositely to one another. The invention furthermore relates to a magnetoresistive magnetic field sensor comprising such an arrangement of layer structures and to a method for producing the arrangement of layer structures and the magnetoresistive magnetic field sensor.