Spin-Valve GMR Sensor With Parallel Permanent Magnet Bias
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Solution Overview
Problem
Conventional magnetic sensors exhibit significant hysteresis in their magnetoresistive (MR) versus external magnetic field curves, which affects their accuracy and linearity.
Innovation Solution
A magnetic sensor design incorporating a spin-valve GMR device with an elongated free layer and a permanent magnet layer, where the permanent magnet layers are arranged parallel to the free layer and separated in a direction intersecting its longitudinal direction, applying a bias magnetic field to suppress hysteresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetoresistive devices are used, then the device structure is simple, but the hysteresis in the MR vs. external magnetic field curve is large
Solution Approach 1:
A permanent magnet layer is introduced as an intermediary component between the external magnetic field source and the spin-valve GMR device. This permanent magnet layer generates a bias magnetic field that acts on the free layer, suppressing hysteresis in the MR curve. The permanent magnet layer serves as a mediator that modifies the magnetic field environment to improve measurement precision without requiring complex control systems.
Solution Approach 2:
The invention changes the magnetic field parameters by introducing a permanent magnet layer that generates a specific bias magnetic field. By adjusting the magnetization direction and magnitude of the permanent magnet layer, the bias magnetic field parameters are optimized to suppress hysteresis while maintaining device simplicity. This parameter change approach resolves the contradiction between measurement precision and device complexity.
2Measurement precision
If a permanent magnet layer is added to apply bias magnetic field, then hysteresis is suppressed, but the device complexity increases
Solution Approach 1:
The magnetic field application function is segmented from the main GMR device structure. The permanent magnet layer is separated as an independent component with its own magnetization control, allowing it to provide bias magnetic field while the spin-valve structure maintains its sensitivity. This segmentation enables hysteresis suppression without significantly complicating the core sensing mechanism.
Solution Approach 2:
The permanent magnet layer serves multiple functions: it provides the bias magnetic field to suppress hysteresis, defines the easy axis of magnetization for the free layer, and can be integrated with existing magnetic field generation structures. This multi-functionality reduces the need for additional components, thereby limiting the increase in device complexity while achieving improved linearity.
3Power
If the permanent magnet layer is arranged parallel to the free layer, then the bias magnetic field is efficiently applied, but the manufacturing precision requirements increase
Solution Approach 1:
The permanent magnet layer is positioned asymmetrically relative to the free layer, with optimization focused on the magnetic field interaction geometry rather than perfect symmetry. The longitudinal directions are arranged parallel to each other, creating an asymmetric but functionally optimized configuration that efficiently applies bias magnetic field while allowing tolerance in manufacturing alignment.
Solution Approach 2:
The invention changes the geometric parameters of the permanent magnet layer and its positioning to optimize magnetic field efficiency. By adjusting the longitudinal direction alignment and separation distance, the bias magnetic field efficiency is maximized while maintaining manufacturability. These parameter optimizations balance the trade-off between power efficiency and manufacturing precision requirements.
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 design effectively reduces hysteresis in the MR versus external magnetic field curve, enhancing linearity and magnetic field isotropy, while allowing for efficient application of the bias magnetic field to the free layer.
Implementation Method 1
the permanent magnet layer efficiently applies a bias magnetic field to the free layer
Implementation Method 2
The present invention relates to a magnetic sensor utilizing a magnetoresistive effect
Implementation Method 3
a spin-valve GMR device including a free layer
Data Source
AI summary
The magnetic sensor comprises a spin-valve GMR including a free layer having an elongated form as seen in a laminating direction and a permanent magnet layer having an elongated form as seen in the laminating direction. The permanent magnet layer is arranged in parallel with the free layer.