Magnetoresistive Sensor Element With Dipolar Layer for Out-of-Plane Sensing
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Solution Overview
Problem
Existing magnetoresistive elements face limitations in increasing out-of-plane sensitivity without complicating the fabrication process or degrading magnetic and temperature stability, primarily due to the demagnetization field at the sense layer's surfaces and the exchange spring effect.
Innovation Solution
Incorporating a dipolar assisting layer that generates an out-of-plane stray field, amplifying the external magnetic field and enhancing sensitivity by up to 50% without increasing the sense layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sense layer thickness is increased to improve out-of-plane sensitivity, then sensitivity increases, but fabrication complexity increases and magnetic stability degrades
Solution Approach 1:
A dipolar assisting layer is introduced as an intermediary component between the sense layer and the external environment. This layer generates a dipolar stray field that amplifies the external magnetic field acting on the sense layer, thereby increasing out-of-plane sensitivity without requiring changes to the sense layer thickness or fabrication process complexity.
2Measurement precision
If the magnetization saturation of the sense layer is decreased to improve out-of-plane sensitivity, then sensitivity increases, but magnetic and temperature stability deteriorate
Solution Approach 1:
The dipolar assisting layer serves as a mediator that provides field amplification through its dipolar stray field. This allows the sense layer to maintain its original magnetization saturation and stability properties while still achieving enhanced sensitivity through the amplified effective magnetic field produced by the assisting layer.
Solution Approach 2:
The invention changes the magnetic field parameter by introducing a dipolar stray field component that constructively adds to the external magnetic field. This parameter change (field amplification) achieves sensitivity enhancement without requiring changes to the sense layer's material composition or magnetization saturation, thereby preserving stability.
3Measurement precision
If the TMR of the MR element is increased to improve out-of-plane sensitivity, then sensitivity increases, but there is little room for further increase
Solution Approach 1:
Instead of further increasing TMR which has reached its practical limits, the dipolar assisting layer is introduced as an alternative mechanism for sensitivity enhancement. The assisting layer provides field amplification through dipolar stray field, offering a new degree of freedom for improving sensitivity without being constrained by TMR saturation.
4Measurement precision
If the diameter of the MR element is decreased to improve out-of-plane sensitivity, then sensitivity may increase, but fabrication complexity increases
Solution Approach 1:
The dipolar assisting layer provides a method for sensitivity enhancement that does not require reducing the MR element diameter. By introducing this intermediary layer that generates dipolar stray field, the invention achieves sensitivity improvement while maintaining larger, easier-to-fabricate element dimensions.
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 dipolar assisting layer significantly increases the out-of-plane sensitivity of the magnetoresistive element by up to 50% while maintaining stability and simplicity in fabrication.
Implementation Method 1
a dipolar assisting layer, configured to generate a dipolar stray field oriented substantially out-of-plane, such that the dipolar stray field is added to the out-of-plane external magnetic field resulting in an effective magnetic field that is larger than and proportional to the external magnetic field
Implementation Method 2
The MR element typically further comprises an interface layer 24, comprising or made of CoFeB, between the tunnel barrier layer 22 and the sense layer 23. The interface layer 24 allows for obtaining a high TMR of the MR element (TMR ratio equal or above than 100%).
Data Source
AI summary
The present disclosure concerns a magnetoresistive sensor (MR) element, comprising a reference layer having a reference magnetization; a sense layer having a sense magnetization comprising a vortex configuration stable under the presence of an external magnetic field, the sense magnetization being reversibly movable in a direction out-of-plane relative to the reference magnetization when the external magnetic field varies in a direction out-of-plane; and a tunnel barrier layer between the reference layer and the sense layer. The MR element further comprises a dipolar assisting layer, configured to generate a dipolar stray field oriented substantially out-of-plane, such that the dipolar stray field is added to the out-of-plane external magnetic field, resulting in an effective magnetic field that is larger than and proportional to the external magnetic field. The present disclosure further concerns a magnetic sensor device comprising the MR element.