Magnetoresistive Sensor Shielding for In-Plane Field Interference
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Solution Overview
Problem
Magnetoresistive sensors with out-of-plane magnetization are sensitive to external in-plane magnetic fields, leading to measurement inaccuracies, particularly in environments with strong interfering fields.
Innovation Solution
Incorporating a soft-magnetic shield adjacent to the layer stack to generate an opposing magnetic field that neutralizes in-plane fields, maintaining the stability of the free layer's magnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetoresistive sensor uses out-of-plane magnetization in the reference layer and vortex magnetization in the free layer to achieve high sensitivity and stability, then the sensor can effectively detect external out-of-plane magnetic fields, but the sensor becomes sensitive to external in-plane magnetic fields which destabilize the free layer magnetization and cause measurement inaccuracies
Solution Approach 1:
A soft-magnetic shield layer is introduced as an intermediary component between the external environment and the free layer. This shield layer has high magnetic permeability and selectively interacts with in-plane magnetic fields, guiding them away from the free layer while leaving out-of-plane fields unaffected. The shield acts as a mediator that filters harmful in-plane fields without interfering with the desired out-of-plane field detection
Solution Approach 2:
The magnetic shielding property is applied locally only to in-plane fields while maintaining transparency to out-of-plane fields. The soft-magnetic shield layer is positioned adjacent to the free layer and configured with specific magnetic properties that create different interactions for different field orientations, providing selective protection where needed without affecting the primary sensing function
2Measurement precision
If a soft-magnetic shield is added to reduce sensitivity to in-plane magnetic fields, then measurement accuracy is improved, but the device complexity and structural configuration become more complex
Solution Approach 1:
The magnetic permeability parameter of the shield layer is optimized to achieve effective shielding with minimal structural complexity. By carefully selecting the magnetic properties and thickness of the soft-magnetic layer, the patent achieves high shielding effectiveness without requiring complex multi-layer structures or additional components
Solution Approach 2:
The soft-magnetic shield layer serves multiple functions simultaneously: it shields against in-plane magnetic fields, maintains the stability of vortex magnetization in the free layer, and does not interfere with out-of-plane field detection. This multi-functionality reduces the need for separate components for each function, thereby reducing overall device complexity
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
The soft-magnetic shield enhances measurement accuracy and sensitivity by minimizing the influence of interfering in-plane fields without increasing the sensor's footprint.
Implementation Method 1
a soft-magnetic shield arranged adjacent to the layer stack and configured to reduce an influence of an external (in-plane, IP) magnetic field along a shielding axis on the free layer
Implementation Method 2
Soft-magnetic materials are distinguished by high magnetic permeability, which means that they are easily able to amplify and conduct external magnetic fields
Implementation Method 3
Magnetoresistive sensors, in particular those based on the principle of tunneling magnetoresistance (TMR)
Data Source
AI summary
A magnetoresistive sensor includes a layer stack containing at least one reference layer having a reference magnetization perpendicular to the plane of the layer stack and at least one free layer having a vortex magnetization. The magnetoresistive sensor furthermore includes at least one soft-magnetic shield arranged adjacent to the layer stack and configured to reduce an influence of an external magnetic field along a shielding axis on the free layer.