Magnetoresistance Element Multi-Dimensional Sensing Bias Stack
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Solution Overview
Problem
Magnetic field sensors, particularly magnetoresistance elements, face challenges in effectively sensing magnetic fields in multiple dimensions due to limitations in their axis of maximum sensitivity orientation and responsiveness to external magnetic fields, which affects their accuracy and applicability in various applications.
Innovation Solution
The design incorporates a magnetoresistance element with a free layer and a bias stack configured to bias the magnetic alignment to a specific direction in the absence of an external magnetic field, combined with a reference stack orthogonal to it, and a three-dimensional magnetic field sensor structure with TMR and GMR elements positioned to detect magnetic fields in multiple dimensions, allowing for enhanced sensitivity and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional spin valve with reference layer and free layer is used, then the magnetic field sensing function is achieved, but the sensitivity and responsiveness to external magnetic fields are limited due to single-axis orientation
Solution Approach 1:
The magnetoresistance element is segmented into functionally distinct stacks: a reference stack with a reference layer having fixed magnetic alignment, a free layer with variable magnetic alignment responsive to external fields, and a bias stack with bias layers providing weak magnetic coupling to establish a predetermined default alignment. This segmentation allows each component to specialize in a specific function, improving overall sensing precision and enabling multi-dimensional detection capabilities.
Solution Approach 2:
The invention transitions from conventional single-axis magnetic field sensing to multi-dimensional sensing by orienting the reference layer and free layer in different spatial dimensions. The reference layer provides a fixed reference direction while the free layer responds to fields in orthogonal directions, enabling the sensor to detect magnetic field vectors in multiple dimensions simultaneously, thereby enhancing both precision and adaptability.
2Measurement precision
If bias layers are added to generate a predetermined magnetic alignment, then the default orientation control is improved, but the device complexity increases
Solution Approach 1:
Bias layers are introduced as intermediary magnetic components positioned between the reference layer and free layer. These bias layers provide weak magnetic coupling that establishes a predetermined default alignment for the free layer in the absence of external fields. The weak coupling ensures that external magnetic fields can still effectively override the bias and realign the free layer, while the intermediary structure maintains relative simplicity by using standard magnetic layer materials and deposition techniques.
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 enables improved sensitivity and responsiveness to magnetic fields in multiple dimensions, enhancing the accuracy and applicability of magnetic field sensors in applications such as angle sensing, current sensing, and rotation detection.
Implementation Method 1
These elements have an electrical resistance that changes in the presence of an external magnetic field
Implementation Method 2
Spin valves are a type of magnetoresistance element formed from two or more magnetic materials or layers
Implementation Method 3
The magnetic coupling between the bias layers and the free layer is relatively weak so that an external field can override the bias and realign the magnetic alignment of the free layer
Implementation Method 4
The bias may be generated by one or more magnetic layers (bias layers) that are magnetically coupled to the free layer
Data Source
AI summary
A magnetoresistance structure includes a first magnetoresistance element and a second magnetoresistance element, wherein the first magnetoresistance element is formed on a surface of the second magnetoresistance element. The first magnetoresistance element comprises a free layer, a bias stack configured to bias a magnetic alignment of the free layer to a first direction in the absence of an external magnetic field, and a reference stack having a reference direction substantially orthogonal to the first direction. The magnetoresistance structure may be used to form a two- or three-dimensional magnetic field sensor.