Magnetic Angular Sensor With Aligned Anisotropy For Low Error
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Solution Overview
Problem
Magnetic angular sensors face angular errors due to finite magnetic anisotropy in the sense layer and pinning strength of the reference layer, limiting their operational margin at low and high external magnetic field magnitudes.
Innovation Solution
The magnetic angular sensor device incorporates a ferromagnetic sense layer with in-plane uniaxial sense magnetic anisotropy, where the easy axis is aligned substantially parallel to the pinning direction, minimizing angular deviation in the sense magnetization alignment within a range of external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the sense layer has finite magnetic anisotropy, then the sensor can operate at low external magnetic fields, but angular error increases at low field magnitudes
Solution Approach 1:
The patent changes the magnetic anisotropy parameter of the sense layer by introducing in-plane uniaxial anisotropy with an easy axis aligned substantially parallel to the pinning direction. This parameter modification enables the sense magnetization to maintain better alignment with the external magnetic field at low field magnitudes, reducing angular error while preserving low-field operation capability
2Ease of manufacture
If the reference layer has finite pinning strength, then the sensor structure remains practical, but angular error increases at high external field magnitudes
Solution Approach 1:
The patent modifies the magnetic configuration by aligning the easy axis of in-plane uniaxial anisotropy in the sense layer substantially parallel to the pinning direction of the reference layer. This parameter change creates a more stable magnetic configuration that reduces the angular error at high external field magnitudes while maintaining practical manufacturability
3Measurement precision
If the easy axis of sense magnetic anisotropy is aligned parallel to the pinning direction, then angular error is minimized, but the sensor configuration becomes more specific and complex
Solution Approach 1:
The patent applies local quality by introducing in-plane uniaxial anisotropy specifically in the sense layer with its easy axis aligned substantially parallel to the pinning direction, while keeping the reference layer configuration standard. This localized modification achieves reduced angular error without requiring complex changes to the entire sensor structure
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 allows for accurate measurement of external magnetic field angles with low angular error, particularly within a range of 200 Oe to 900 Oe, achieving an angular error of less than 0.5°, thereby enhancing the operational margin of the sensor.
Implementation Method 1
Tunnel magnetoresistance (TMR) effect is employed to sense the relative angle between the magnetization of the sensing layer and the magnetization of the reference layer, and thus to measure a direction of an external magnetic field
Implementation Method 2
Pinning the reference magnetization 230 can be achieved by a pinning layer 24 (such as an antiferromagnetic layer) exchange coupled to the reference magnetization 230
Data Source
AI summary
Magnetic angular sensor device destined to sense an external magnetic field, the sensor device including a plurality of magnetic sensor elements, each sensor element including a magnetic tunnel junction containing a ferromagnetic reference layer having a reference magnetization that is pinned in a pinning direction, a ferromagnetic sense layer having a sense magnetization that can be oriented in an external magnetic field, and a tunnel barrier spacer layer, between the reference layer and the sense layer; wherein the sense layer of at least a portion of said plurality of sensor elements comprises an in-plane uniaxial sense magnetic anisotropy having an easy axis that is aligned substantially parallel to the pinning direction, such that an angular deviation in the alignment of the direction of the sense magnetization in the external magnetic field is minimized for a range of external magnetic field.