Magnetoresistive Sensor With Perpendicular Anisotropy for Z-Direction Detection
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Solution Overview
Problem
Magnetoresistive sensors, such as xMR sensors, have limitations in their operating range in low linear magnetic fields and lack sensitivity in the z-direction, making them less effective compared to Hall sensors.
Innovation Solution
The implementation of a layer stack with a reference layer and a magnetically free layer, where one orientation is in-plane and the other is out-of-plane, and a metal multilayer is either adjacent or constitutes the magnetically free layer, enabling sensitivity in the z-direction while maintaining a high linear field range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional xMR sensor designs are used, then in-plane sensitivity is achieved, but z-direction sensitivity is lost
Solution Approach 1:
The patent introduces a metal multilayer structure that generates perpendicular magnetic anisotropy, enabling the magnetically free layer to detect magnetic fields in the z-direction (perpendicular to the film plane). This dimensional transition from in-plane to out-of-plane magnetization allows the sensor to detect z-direction fields while maintaining xMR effect functionality.
Solution Approach 2:
The patent employs a composite layer stack consisting of ferromagnetic layers, nonmagnetic spacer layers, and metal multilayers (such as CoFeB/MgO or Co/Pt). This composite structure combines the magnetic properties of ferromagnetic materials with the perpendicular anisotropy induced by metal multilayers, achieving both z-direction sensitivity and high linear range.
2Measurement precision
If cross-geometric xMR sensors are designed to achieve z-sensitivity, then z-direction detection is enabled, but signal output and linear field range deteriorate
Solution Approach 1:
The patent optimizes the thickness and composition of the magnetically free layer and metal multilayer to achieve the desired perpendicular magnetic anisotropy strength. By carefully controlling parameters such as layer thickness (e.g., 3-5 nm for CoFeB), composition ratios, and metal multilayer structure, the sensor achieves both high z-direction sensitivity and maintained linear field range.
Solution Approach 2:
The patent applies different material compositions and structures to specific layers within the stack. The magnetically free layer has optimized composition for perpendicular magnetization, while the reference layer maintains stable in-plane magnetization. This local differentiation of material properties enables the sensor to simultaneously achieve z-direction sensitivity and high signal output.
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 enhances the sensitivity and linear range of magnetoresistive sensors, potentially tripling the usable xMR effect and making them more suitable for z-sensitive magnetic field detection.
Implementation Method 1
The magnetically free magnetization has a second magnetic orientation in a ground state. One of the first or the second magnetic orientation is oriented in-plane and the other is oriented out-of-plane
Implementation Method 2
Magnetic field sensors based on the magnetoresistance effect, so-called magnetoresistive sensors, are often used. xMR sensors can detect the orientation of an applied magnetic field by measuring sine and cosine angle components
Data Source
AI summary
Example implementations are concerned with magnetoresistive sensors and with corresponding fabrication methods for magnetoresistive sensors. One example here relates to a magnetoresistive sensor having a layer stack. The layer stack comprises a reference layer having a reference magnetization, which is fixed and has a first magnetic orientation. The layer stack comprises a magnetically free layer. The magnetically free layer has a magnetically free magnetization. The magnetically free magnetization is variable in the presence of an external magnetic field. The magnetically free magnetization has a second magnetic orientation in a ground state. One of the first or the second magnetic orientation is oriented in-plane and the other is oriented out-of-plane. The layer stack comprises a metal multilayer. In this case, either the metal multilayer is arranged adjacent to the magnetically free layer, or the metal multilayer constitutes the magnetically free layer.