Magnetic Detector Full-Bridge Circuit Exchange Coupling

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Solution Overview

Problem

Existing magnetic detectors with full-bridge circuits using magnetoresistive sensors face challenges in achieving high detection accuracy and resistance to strong magnetic fields, particularly in miniaturization and independent bias magnetic field settings for each sensor.

Innovation Solution

The magnetic detector employs a full-bridge circuit with two magnetoresistive sensors on the same substrate, utilizing pinning and biasing antiferromagnetic layers with different blocking temperatures to generate exchange coupling magnetic fields, allowing for flexible setting of fixed magnetization axes and bias magnetic fields without external magnetic field application, enhancing resistance to strong magnetic fields and miniaturization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetoresistive sensors are arranged in a full-bridge circuit on the same substrate, then detection accuracy is improved, but mutual interference between sensors increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidmutual interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by giving each magnetoresistive sensor distinct magnetic field characteristics through different pinned layer orientations. Sensors are designed with specific magnetization directions (e.g., first sensor with magnetization in x-direction, second sensor with magnetization in y-direction) so that each responds preferentially to magnetic fields in its designated direction, thereby reducing mutual interference while maintaining full-bridge circuit benefits for enhanced detection accuracy

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If external magnetic fields are applied to set magnetization directions, then fixed magnetization axes are established, but resistance to strong magnetic fields is reduced

Engineering Contradiction:

Improvefixed magnetization axisVSAvoidresistance to strong magnetic field

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent employs preliminary action by using exchange coupling between pinned magnetic layers and antiferromagnetic layers to pre-establish stable magnetization directions during the manufacturing process. The pinned layers are magnetized in desired directions (x, y, or z directions) through exchange coupling with antiferromagnetic layers during fabrication, creating permanently fixed magnetization axes that are resistant to subsequent external magnetic field disturbances during sensor operation

Inventive Principle:

Principle #10Preliminary action

3Area of stationary object

If sensors are miniaturized on the same substrate, then device size is reduced, but independent bias magnetic field settings become difficult

Engineering Contradiction:

Improvedevice sizeVSAvoidindependent bias magnetic field setting

Core Design Contradiction:

Area of stationary objectVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by providing each magnetoresistive sensor with its own bias magnetic field generation means (such as permanent magnets or current-carrying conductors) positioned in close proximity to the sensor. This localized bias field generation allows each miniaturized sensor to be independently biased without requiring large external magnetic field sources, enabling independent control of bias fields for each sensor while maintaining compact device dimensions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements nesting by integrating bias magnetic field generation means directly within or immediately adjacent to each magnetoresistive sensor structure. The bias field generators (permanent magnets or conductors) are nested within the overall sensor assembly, allowing independent bias field settings for each sensor while minimizing the total device area and maintaining miniaturization

Inventive Principle:

Principle #7Nested doll (Nesting)

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 improves detection accuracy and resistance to strong magnetic fields while allowing for miniaturization of the magnetic detector, as the sensors have distinct responsiveness to external magnetic fields and are less influenced by each other.

Implementation Method 1

utilizing pinning and biasing antiferromagnetic layers with different blocking temperatures to generate exchange coupling magnetic fields

Methodology Applied

Scientific EffectExchange coupling: Magnetism

Implementation Method 2

magnetic detectors with full-bridge circuits using magnetoresistive sensors

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS11415644B2Magnetic detector and method for producing the same

Publication Date: 2022.08.16 ALPS ALPINE CO LTD

AI summary

A magnetic detector includes a full-bridge circuit including magnetoresistive sensors on the same substrate. The magnetoresistive sensors include two magnetoresistive films and have different relationships between the fixed magnetization direction and the bias application direction. The fixed magnetization direction and the bias application direction are determined with three or more exchange coupling films including antiferromagnetic layers with different blocking temperatures. Thus, the magnetic detector has high resistance to a strong magnetic field, is easy to produce, and has a high degree of flexibility in production.