Magnetic Sensor with Low Magnetization Free Layer for Wide Range Detection
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Solution Overview
Problem
Conventional magnetic sensors have a limited detected magnetic field range of about 2 mT, making them ineffective for larger external magnetic fields.
Innovation Solution
A magnetic sensor design featuring a magnetization fixed layer, a magnetic field detecting layer with a changing magnetization direction, and an intermediate layer with resistance dependent on the angle between the fixed and detecting layers, where the magnetization amount per unit area of the detecting layer is less than 0.2 memu/cm², allowing for a larger detected magnetic field range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias magnet film is used to apply bias magnetic field to the free layer, then the magnetization direction of the free layer is stably restored to initial state, but the detected magnetic field range is limited to only about 2 mT
Solution Approach 1:
The patent changes the magnetization amount per unit area of the free layer from conventional values to specifically less than 0.2 emu/cm². This parameter change enables the free layer to respond to much larger external magnetic fields (300 mT or more) while still maintaining stable magnetization restoration through the bias magnet film, thus resolving the contradiction between stability and detection range.
2Measurement precision
If the magnetization amount per unit area of the free layer is increased to improve detection sensitivity, then the response to external magnetic field improves, but the detected magnetic field range becomes limited
Solution Approach 1:
The patent identifies and optimizes the magnetization amount per unit area parameter of the free layer, setting it to less than 0.2 emu/cm². This specific parameter value achieves an optimal balance where the free layer maintains sufficient sensitivity to detect external magnetic fields while extending the detectable range to 300 mT or more, overcoming the traditional trade-off between sensitivity and range.
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 magnetic sensor achieves a detected magnetic field range of 300 mT or more, enhancing its capability to handle larger external magnetic fields without material or crystal state dependencies.
Implementation Method 1
The intermediate layer is disposed between the magnetization fixed layer and the magnetic field detecting layer and has a resistance value that changes depending on an angle between the magnetization direction of the magnetization fixed layer and the magnetization direction of the magnetic field detecting layer
Data Source
AI summary
A magnetic sensor includes a magnetization fixed layer, a magnetic field detecting layer, and an intermediate layer. The magnetization fixed layer is formed into a thin-film shape, and a magnetization direction of the magnetization fixed layer is fixed in a direction parallel to an in-plane direction. A magnetization direction of the magnetic field detecting layer changes depending on an external magnetic field. The intermediate layer is disposed between the magnetization fixed layer and the magnetic field detecting layer, and a resistance value of the intermediate layer changes depending on an angle between the magnetization direction of the magnetization fixed layer and the magnetization direction of the magnetic field detecting layer. A magnetization amount per unit area of the magnetic field detecting layer is less than 0.2 [memu/cm2].