Magnetic Sensor Cell With Perpendicular Anisotropy for Linear Field Sensing
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Solution Overview
Problem
Existing magnetic sensor cells face challenges in accurately sensing one- and two-dimensional external magnetic fields due to non-linear and hysteretic behavior, particularly in aligning sense magnetization perpendicular to reference magnetization, which affects the measurement of magnetic field components.
Innovation Solution
A magnetic sensor cell with a magnetic tunnel junction comprising a reference layer, a sense layer, and a tunnel barrier layer, where the sense layer has intrinsic anisotropy perpendicular to the plane, an anisotropy field above 150 Oe, and a tunnel barrier thickness between 1 nm and 3 nm, allowing for high tunnel magnetoresistance and precise alignment of sense magnetization, enabling effective measurement of in-plane and out-of-plane magnetic field components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sense magnetization is aligned perpendicular to the reference magnetization to achieve linear sensing, then measurement precision is improved, but device complexity increases due to the need for precise orientation control
Solution Approach 1:
The patent changes the magnetic anisotropy parameter of the sense layer from in-plane to perpendicular anisotropy by modifying material composition and layer thickness. This parameter change enables the sense magnetization to be naturally perpendicular to the reference magnetization without complex orientation control mechanisms, achieving linear sensing while simplifying device structure
Solution Approach 2:
The patent transitions the sense magnetization orientation from the in-plane dimension to the out-of-plane dimension by introducing perpendicular magnetic anisotropy. This dimensional change allows the sense layer to respond linearly to in-plane magnetic fields while maintaining a simple planar device structure, resolving the contradiction between measurement precision and device complexity
2Measurement precision
If the tunnel barrier layer thickness is reduced to increase tunnel magnetoresistance, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the tunnel barrier layer thickness to a specific range (1-3 nm) and modifies the material composition to achieve high tunnel magnetoresistance (>50%) without requiring extremely thin barriers. This parameter optimization balances measurement precision with manufacturability, avoiding the need for ultra-precise thin film deposition
Solution Approach 2:
The patent employs composite material structures including CoFeB/CoFe multilayers and MgO tunnel barriers with specific thickness ratios. These composite structures enhance tunnel magnetoresistance through interfacial effects and spin scattering mechanisms, allowing adequate TMR values with manufacturable barrier thicknesses that reduce precision requirements
3Reliability
If the anisotropy field is increased to improve sense layer stability, then reliability is improved, but the ability to align sense magnetization with external fields decreases
Solution Approach 1:
The patent carefully balances the perpendicular anisotropy field strength and layer thickness parameters to achieve optimal performance. By adjusting these parameters within specific ranges, the sense layer maintains sufficient stability while remaining responsive to external magnetic fields, resolving the contradiction between reliability and adaptability
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 solution provides linear and non-hysteretic sensing of magnetic fields, enabling accurate measurement of one- and two-dimensional external magnetic fields with improved signal-noise ratio and robustness, overcoming the limitations of existing technologies.
Implementation Method 1
a tunnel barrier layer between the sense and reference layers; the sense layer comprising an intrinsic anisotropy being substantially perpendicular to the plane of the sense layer such that the sense magnetization is orientable
Implementation Method 2
the sense layer comprising an intrinsic anisotropy being substantially perpendicular to the plane of the sense layer such that the sense magnetization is orientable between an initial direction perpendicular to the plane of the sense layer and a direction parallel to the plane of the sense layer
Implementation Method 3
During a sensing operation, an external magnetic field aligns the sense magnetization more parallel or more antiparallel to the reference magnetization
Data Source
Figure 1(a)~2
Figure 3~4(b)
Figure 5(a)~5(b)
AI summary
The present disclosure concerns a magnetic sensor cell (1) comprising a magnetic tunnel junction (2) comprising a reference layer (23) having a reference magnetization (230) oriented substantially parallel to the plane of the reference layer (23), a sense layer (21) having a sense magnetization (210), and a tunnel barrier layer (22) between the sense and reference layers (21, 23); the sense layer (21) comprising an intrinsic anisotropy being substantially perpendicular to the plane of the sense layer (21) such that the sense magnetization (210) is orientable between an initial direction perpendicular to the plane of the sense layer (21) and a direction parallel to the plane of the sense layer (21);the intrinsic anisotropy having in anisotropy field being above 150 Oe.