TMR Sensor Vortex Stack for Transfer-Curve Linearity
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Solution Overview
Problem
Magnetic field sensors, particularly those using TMR elements, suffer from non-linear transfer curves and sensitivity errors due to the magnetic alignment of the free layer responding to external fields, leading to inaccuracies in sensing applications.
Innovation Solution
Incorporating a magnetic vortex in the free layer of TMR elements and using an antiferromagnetic bias layer to offset the transfer curves, enhancing linearity and reducing errors by configuring the elements in Wheatstone or half bridges with opposite pinning directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional TMR element with a free layer is used, then the sensor can detect magnetic fields, but the transfer curve is non-linear causing sensitivity errors and measurement inaccuracies
Solution Approach 1:
The free layer is segmented into multiple sub-layers with different magnetic properties. By dividing the free layer into distinct magnetic sub-layers, each with controlled magnetization directions, the overall transfer curve linearity is improved while maintaining the magnetoresistive sensing function
Solution Approach 2:
The patent uses composite magnetic structures combining ferromagnetic layers with different anisotropies and antiferromagnetic coupling layers. This composite approach creates a free layer with tailored magnetic characteristics that produce a linear transfer curve response to external magnetic fields
2Adaptability or versatility
If the free layer magnetization aligns with external fields, then the sensor responds to magnetic field changes, but this causes non-linear transfer curves and sensitivity errors
Solution Approach 1:
Different regions of the free layer are given different magnetic qualities through the multi-layer structure. Each sub-layer has locally optimized magnetic properties (different anisotropies, thicknesses, and compositions) that collectively produce a linear response while maintaining overall magnetic field adaptability
Solution Approach 2:
The patent modifies magnetic parameters such as layer thickness, composition ratios, and anisotropy strengths to tune the magnetization behavior. By carefully adjusting these parameters, the transfer curve linearity is optimized while preserving the sensor's ability to respond to external magnetic fields
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 proposed solution significantly reduces linearity deviations and sensitivity errors, improving the accuracy and reliability of magnetic field sensors by shifting the transfer curves and enhancing the output signal linearity.
Implementation Method 1
a bias layer to offset the vortex by magnetic bias
Implementation Method 2
the vortex layer is configured for exchange bias
Implementation Method 3
These elements have an electrical resistance that changes in the presence of an external magnetic field
Implementation Method 4
Spin valves are a type of magnetoresistance element formed from two or more magnetic materials or layers
Implementation Method 5
a free layer having a vortex layer to provide a magnetic vortex
Data Source
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AI summary
Methods and apparatus for devices including TMR elements with a free layer having a vortex layer to provide a magnetic vortex, a spacer layer, a reference layer, and a bias layer to offset the vortex by magnetic exchange bias. Sensor embodiments increase linearity for enhancing sensor performance.