Magnetic Sensor Antiferromagnetic Biasing Without MR Shielding
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Solution Overview
Problem
Existing magnetic sensors face a reduction in sensitivity due to the use of magnetic field generators that act as shields when closely stacked with magnetoresistive elements, compromising the effectiveness of the bias magnetic field.
Innovation Solution
A magnetic sensor design that includes a magnetoresistive element with a ferromagnetic layer and an insulating layer on both sides, and an antiferromagnetic layer without a magnetic layer between them, allowing for the application of a bias magnetic field without reducing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the distance between the magnetoresistive element and the magnetic field generator is reduced to increase bias magnetic field strength, then the bias magnetic field strength is improved, but the magnetic field generator acts as a shield and reduces sensitivity
Solution Approach 1:
The magnetic field generator is segmented into two separate magnetic layers (first magnetic layer and second magnetic layer) with different magnetization directions. This segmentation allows each layer to contribute differently to the magnetic field, enabling both strong bias field application and maintained sensitivity by preventing shielding effects.
Solution Approach 2:
Different regions of the magnetic field generator are assigned different local properties: the first magnetic layer has magnetization in a first direction while the second magnetic layer has magnetization in a second direction orthogonal to the first. This local quality differentiation enables the system to achieve both strong bias field strength and maintained sensitivity simultaneously.
2Force
If the size of the magnetic field generator is increased to increase bias magnetic field strength, then the bias magnetic field strength is improved, but the magnetic field generator acts as a shield and reduces sensitivity
Solution Approach 1:
The magnetic field generator is divided into two functional segments (first magnetic layer and second magnetic layer) with orthogonal magnetization directions. This segmentation allows the generator to provide strong bias field while maintaining sensitivity by distributing the magnetic function across different oriented layers.
Solution Approach 2:
Different portions of the magnetic field generator exhibit different local magnetic qualities through orthogonal magnetization directions in the first and second magnetic layers, enabling simultaneous achievement of high bias field strength and preserved sensitivity without requiring overall size increase.
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 maintains the sensitivity of the magnetoresistive element by preventing the magnetic field generator from acting as a shield, ensuring effective bias magnetic field application.
Implementation Method 1
an antiferromagnetic layer disposed on the at least one magnetoresistive element, the first ferromagnetic layer, and the insulating layer. The antiferromagnetic layer includes a first antiferromagnetic portion that faces the first ferromagnetic layer
Implementation Method 2
at least one magnetoresistive element including a plurality of magnetic films stacked on each other
Data Source
AI summary
A magnetic sensor includes at least one MR element, a ferromagnetic layer disposed to overlap the at least one MR element when viewed in a first direction, an insulating layer disposed on both sides of the at least one MR element in a second direction, and an antiferromagnetic layer disposed on the at least one MR element, the ferromagnetic layer, and the insulating layer. The antiferromagnetic layer includes an antiferromagnetic portion that faces the ferromagnetic layer, and a non-facing part that faces the at least one MR element and the insulating layer but does not face the ferromagnetic layer. No magnetic layer is present between the at least one MR element and the antiferromagnetic layer.