Magnetometric Sensor Lattice Mismatch Reduction
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Solution Overview
Problem
Magnetometric sensors used in electric vehicles and hybrid cars face a reduction in detection sensitivity when stored at high temperatures due to exchange coupling bias, leading to decreased measurement accuracy and reliability.
Innovation Solution
A magnetometric sensor with a layered structure comprising a fixed magnetic layer, a free magnetic layer, and a nonmagnetic material layer, where the free magnetic layer includes a misfit-reducing sub-layer and a second free magnetic sub-layer ferromagnetically coupled to the first free magnetic sub-layer, reducing lattice mismatch and maintaining detection sensitivity even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exchange coupling bias is applied to align magnetization direction in the free magnetic layer, then measurement accuracy is improved, but detection sensitivity decreases during long-term storage at high temperatures
Solution Approach 1:
A nonmagnetic intermediate sub-layer is introduced between the fixed magnetic layer and the free magnetic layer. This intermediate layer acts as a mediator that reduces the harmful exchange coupling bias between the fixed and free magnetic layers, thereby preventing sensitivity degradation during high-temperature storage while still allowing the bias field to function for measurement accuracy
Solution Approach 2:
The patent employs a composite layered structure consisting of multiple magnetic and nonmagnetic layers with specific material compositions. The free magnetic layer itself is composed of multiple sub-layers with different magnetic properties, creating a composite structure that maintains both measurement accuracy and high-temperature stability
2Stability of the object's composition
If a layered structure with antiferromagnetic layer is used to cause exchange coupling bias, then magnetization alignment is improved, but detection sensitivity reduces after high-temperature storage
Solution Approach 1:
The nonmagnetic intermediate sub-layer serves as a buffer that decouples the strong exchange interaction between the antiferromagnetic layer and the free magnetic layer. This intermediate layer allows controlled magnetization alignment while preventing the excessive coupling that leads to sensitivity loss during thermal aging
Solution Approach 2:
The patent applies different material properties and coupling strengths to different regions of the magnetic structure. The intermediate sub-layer creates a gradient in magnetic coupling, allowing local optimization of both alignment stability and sensitivity preservation
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 effectively prevents a decrease in detection sensitivity of the magnetoresistance effect element during long-term storage at high temperatures, enhancing measurement accuracy and reliability.
Implementation Method 1
a first antiferromagnetic layer on the free magnetic layer on the opposite side to the side facing the nonmagnetic material layer to cause an exchange coupling bias between the first antiferromagnetic layer and the free magnetic layer
Implementation Method 2
The free magnetic layer includes a misfit-reducing sub-layer for decreasing the lattice mismatch of the free magnetic layer with the first antiferromagnetic layer
Implementation Method 3
Examples of the magnetism detecting element for the magnetometric sensor include magnetoresistance effect elements such as giant magnetoresistance (GMR) elements
Implementation Method 4
a ferromagnetic sub-layer made of a ferromagnetic material disposed on the opposite side to the side facing the first antiferromagnetic layer
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A magnetometric sensor (1) comprises a plurality of magnetoresistance effect elements (11, 11') having different sensitivity axes on a single substrate. The magnetoresistance effect element (11, 11') has a layered structure, comprising a fixed magnetic layer (21) and a free magnetic layer (23) stacked with a nonmagnetic material layer (22) interposed therebetween, on a substrate (29) and includes a first antiferromagnetic layer (24) on the free magnetic layer (23) on the opposite side to the side facing the nonmagnetic material layer (22) to cause an exchange coupling bias between the first antiferromagnetic layer (24) and the free magnetic layer (23) and align the magnetization direction of the free magnetic layer (23) in a prescribed direction in a state of permitting variation in magnetization. The free magnetic layer (23) includes a first free magnetic sub-layer (23a), a second free magnetic sub-layer (23c) disposed on the first antiferromagnetic layer (24) side with respect to the first free magnetic sub-layer (23a) and ferromagnetically coupled to the first free magnetic sub-layer (23a), and a misfit-reducing sub-layer (23b) disposed between the first free magnetic sub-layer (23a) and the second free magnetic sub-layer (23c) and decreasing the lattice mismatch of the free magnetic layer (23) with the first antiferromagnetic layer (24).