Asymmetric Pinned Layer Geometry for Magnetoresistance Sensor Accuracy
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Solution Overview
Problem
Sensors using magneto-resistance effect elements face challenges in achieving high sensing accuracy due to variations in the magnetization direction of the pinned layer caused by external magnetic fields, which affects the accuracy of detecting the angle of rotation in applications like power steering systems.
Innovation Solution
A magneto-resistance effect element configuration with a pinned layer having a planar shape that is long in the fixed magnetization direction and short in the orthogonal direction, combined with a free layer that can vary its magnetization direction in response to external fields, and an intermediate layer, helps minimize the impact of external magnetic fields on the pinned layer, thereby reducing sensing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional pinned layer configuration is used, then the sensor can detect magnetic fields, but the magnetization direction of the pinned layer varies due to external magnetic fields, reducing sensing accuracy
Solution Approach 1:
The pinned layer is designed with an asymmetric planar shape that is elongated in the direction of the fixed magnetization direction and shortened in the orthogonal direction. This asymmetric geometry creates magnetic anisotropy that stabilizes the magnetization direction along the long axis, making it resistant to variations caused by external magnetic fields applied from other directions.
Solution Approach 2:
The invention applies different geometric characteristics to different spatial dimensions of the pinned layer. By making the layer elongated specifically in the magnetization direction and compact in the orthogonal direction, the local quality of magnetic resistance to field variations is enhanced along the critical magnetization axis while maintaining sensitivity in the detection axis.
2Measurement precision
If the pinned layer is made more resistant to external fields, then sensing accuracy improves, but the device complexity increases due to specific geometric requirements
Solution Approach 1:
The pinned layer employs an asymmetric rectangular planar shape with specific aspect ratio requirements (long side parallel to magnetization direction, short side perpendicular to it). This asymmetric geometry inherently provides magnetic anisotropy that stabilizes the magnetization direction without requiring additional complex structural elements or multiple layers, thus improving accuracy while controlling 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
This configuration enhances the accuracy of the sensor by reducing the likelihood of magnetization direction changes in the pinned layer, leading to improved sensing precision and reduced angular errors in detecting the angle of rotation.
Implementation Method 1
Sensors using magneto-resistance effect (MR) elements have sometimes been used to sense the angle of rotation of a steering wheel
Implementation Method 2
The CIP-GMR element is a giant magneto-resistance effect element including paired ferromagnetic layers and a nonmagnetic layer positioned between the ferromagnetic layers
Implementation Method 3
a pinned layer that is a ferromagnetic layer shaped like a pillar with a desired size and having a fixed magnetization direction
Data Source
AI summary
A magneto-resistance effect element for a sensor to sense a variation in externally applied magnetism includes a pinned layer having a fixed magnetization direction, a free layer having a magnetization direction which varies in response to an external magnetic field, and an intermediate layer provided between the pinned layer and the free layer. The pinned layer has a planar shape which is long in the fixed magnetization direction and which is short in a direction orthogonal to the fixed magnetization direction. Moreover, the pinned layer preferably has a planar shape in which the pinned layer is divided into a plurality of sections.