Vortex Magnetoresistive Sensor Reset Current for Linear Hysteresis

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Solution Overview

Problem

Magnetic sensors with vortex free layers face issues of core displacement obstruction due to defects in the ferromagnetic layer, leading to deteriorated reproducibility and linearity of the hysteresis loop.

Innovation Solution

A magnetic sensor design incorporating a current changing circuit to alter the current value during non-detection periods, ensuring the core displaces smoothly and reproducibly, even with defects, by using a magnetoresistive element with a fixed layer, free layer, and non-magnetic layer, and a control module to manage the current changing circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an indentation is provided to the edge of the free layer to form the core reproducibly, then the reproducibility of the hysteresis loop is improved, but the linearity of the magnetic sensor deteriorates when the core gets caught by defects

Engineering Contradiction:

Improvereproducibility of hysteresis loopVSAvoidlinearity of magnetic sensor

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the physical state of the magnetoresistive element by applying a reset current to transition the free layer magnetization from a vortex state to a uniform state. This parameter change (magnetization configuration) allows the core to be released from defect positions, thereby improving linearity while maintaining reproducibility through controlled state transitions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements periodic resetting of the free layer magnetization by applying reset currents at specific intervals (during non-detection periods). This periodic action prevents the core from being permanently trapped by defects, ensuring both reproducible hysteresis loops and linear response characteristics over time.

Inventive Principle:

Principle #19Periodic action

2Reliability

If the core is allowed to displace and reciprocate along the same path using an indentation, then the reproducibility is improved, but the displacement of the core in accordance with external magnetic field change is obstructed when caught by defects

Engineering Contradiction:

ImprovereproducibilityVSAvoidcore displacement responsiveness

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces a reset current as an intermediary mechanism to mediate between the core position and defect obstructions. By applying this intermediary current, the magnetization state is reset, allowing the core to overcome defect barriers and maintain responsive displacement behavior while preserving reproducible operation paths.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a current changing circuit is used to change the current value, then the core displacement smoothness is improved, but the energy consumption increases during operation

Engineering Contradiction:

Improvecore displacement smoothnessVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The current changing circuit operates periodically rather than continuously, applying reset currents only during non-detection periods. This periodic operation maintains smooth core displacement characteristics while significantly reducing overall energy consumption compared to continuous current application.

Inventive Principle:

Principle #19Periodic 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

Improves the reproducibility and linearity of the hysteresis loop by ensuring the core displaces correctly, reducing hysteresis caused by defects, and enhancing the sensor's responsiveness to external magnetic fields.

Implementation Method 1

Magnetic sensors using magnetoresistive elements including a vortex free layer have been attracting attention

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 2

the vortex free layer forms a vortex with stable magnetization without an external magnetic field

Methodology Applied

Scientific EffectVortex magnetization:

Data Source

PatentUS20260036654A1Magnetic sensor, magnetic sensor controlling method, and magnetic sensor controlling program

Publication Date: 2026.02.05 TDK CORP

AI summary

A magnetic sensor includes: a magnetoresistive element connected between a power source and the ground, having a fixed layer the magnetization of which is fixed, a free layer having a free magnetization that forms a vortex configuration when there is no external magnetic field, and a non-magnetic layer provided between the fixed layer and the free layer; and a current changing circuit for changing a current value of a current flowing through the magnetoresistive element.