Magnetometer Yoke Structure Hard Soft Magnetic Layers

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Solution Overview

Problem

Existing yoke structures for magnetometers suffer from changes in remanent magnetization states due to external field exposure, leading to sensitivity shifts, noise, and reduced effectiveness of initial calibrations.

Innovation Solution

A yoke structure comprising at least one hard magnetic layer and at least one soft magnetic layer, where the first coercivity of the hard magnetic layer is greater than the second coercivity of the soft magnetic layer, providing a stable reset direction for the magnetic material and reducing magnetic domain formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a yoke structure is used to focus and shield external fields from magnetic sensing elements, then sensitivity is improved, but remanent magnetization changes cause sensitivity shifts and noise

Engineering Contradiction:

ImprovesensitivityVSAvoidstability of remanent magnetization

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies composite materials by combining hard magnetic material and soft magnetic material in a single yoke structure. The hard magnetic material provides stable remanent magnetization that resists external field exposure, while the soft magnetic material provides high permeability for effective field shielding and focusing. This composite approach resolves the contradiction by achieving both high sensitivity (through soft magnetic material) and stability (through hard magnetic material).

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by assigning different magnetic properties to different regions of the yoke structure. Specifically, hard magnetic material is placed in regions where stable remanent magnetization is needed to counteract external field exposure, while soft magnetic material is placed in regions where high permeability is needed for field redirection and focusing. This spatial differentiation of material properties allows the yoke to simultaneously achieve sensitivity and stability.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If external field exposure is increased during operation, then the magnetometer must function in varying magnetic environments, but remanent magnetization changes lead to noise and calibration degradation

Engineering Contradiction:

Improveoperation in varying magnetic environmentsVSAvoidnoise and sensitivity shifts

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of external field exposure into a beneficial one by using hard magnetic material that can be deliberately magnetized in a controlled direction. Instead of allowing random remanent magnetization changes that cause noise, the hard magnetic material is programmed to acquire a specific remanent state that actively counteracts the effects of external field exposure, thereby converting the potential harm into a stabilizing benefit.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies preliminary anti-action by pre-magnetizing the hard magnetic material in a specific direction during manufacturing or initialization. This pre-established remanent magnetization creates a baseline magnetic state that counteracts subsequent external field exposures, preventing the harmful remanent changes that would otherwise occur during operation in varying magnetic environments.

Inventive Principle:

Principle #9Preliminary anti-action

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 proposed yoke structure design achieves stable and repeatable magnetometer performance by minimizing changes in remanent magnetization, thereby maintaining sensitivity and reducing noise over the product lifetime.

Implementation Method 1

a first coercivity of the at least one hard magnetic layer is greater than a second coercivity of the at least one soft magnetic layer

Methodology Applied

Scientific EffectCoercivity: Magnetic Hysteresis

Implementation Method 2

Different remanent magnetization states of yoke structure 100 can create large offsets, sensitivity shifts, and noise

Methodology Applied

Scientific EffectRemanent magnetization: Magnetic Hysteresis

Implementation Method 3

a first coercivity of the at least one hard magnetic layer is greater than a second coercivity of the at least one soft magnetic layer

Methodology Applied

Scientific EffectMagnetic permeability: Ferromagnetism

Implementation Method 4

These sensors includes anisotropic magnetoresistance (AMR), giant MR (GMR) and tunneling MR (TMR) sensors

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS12320871B2Yoke structures for magnetometers

Publication Date: 2025.06.03 APPLE INC

AI summary

Embodiments are disclosed for yoke structures for improved magnetometer performance. In an embodiment, a magnetometer comprises: a yoke structure comprising at least one hard magnetic layer and at least one soft magnetic layer arranged along a dimension of the yoke structure, where a first coercivity of the at least one hard magnetic layer is greater than a second coercivity of the at least one soft magnetic layer; and at least one magnetic sensing element located in proximity to the at least one soft magnetic layer. In another embodiment, a magnetometer comprises: a multilayer yoke structure comprising layers of non-magnetic material and magnetic material along a dimension of the yoke structure; and at least one magnetic sensing element located in proximity to the yoke structure.