CPP MR Element Antiparallel Magnetization Verification

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Solution Overview

Problem

There is a need for an examination method to ensure that the magnetization directions of two free layers in a CPP-type magnetoresistance (MR) effect element are antiparallel before the orthogonalizing bias function part starts functioning, as existing methods struggle to reliably achieve this state due to limitations in exchange-coupling and material restrictions.

Innovation Solution

The method involves applying a sense current to the MR effect part with a nonmagnetic middle layer and a first and second ferromagnetic layer, and using an orthogonalizing bias function part to change its magnetization direction between two modes, measuring the output waveform in response to an external magnetic field for each mode, and checking the asymmetry of the waveforms to verify the antiparallel state of the magnetization directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If exchange-coupling is used to make magnetization directions antiparallel, then the magnetization state can be controlled, but the method is limited by material restrictions and cannot reliably achieve the desired state

Engineering Contradiction:

Improvereliability of achieving antiparallel magnetization stateVSAvoidflexibility in achieving magnetization state

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces a bias magnet as an intermediary component that generates a magnetic field to assist in forming the antiparallel magnetization state between the two ferromagnetic layers. This mediator overcomes the limitations of direct exchange-coupling by providing an external magnetic field that enables reliable antiparallel alignment without being constrained by material restrictions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies a magnetic field from the bias magnet before the orthogonalizing bias function part is activated to preliminarily establish the antiparallel magnetization state. This preliminary action ensures that the magnetization directions are properly aligned before the main operational bias is applied, improving reliability of the overall system

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If the orthogonalizing bias function part is activated, then the magnetization directions can be orthogonalized, but there is no method to examine whether the antiparallel state is achieved before activation

Engineering Contradiction:

Improveprecision of magnetization state examinationVSAvoidease of examining magnetization state

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent implements a feedback mechanism by measuring the resistance value of the MR element and comparing it against a predetermined threshold. This feedback loop allows the system to determine whether the antiparallel magnetization state has been achieved, providing precise measurement capability

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses the MR element's own resistance value as the examination criterion. By measuring the resistance of the element itself and comparing it to the threshold, the system performs self-examination without requiring external complex measurement equipment, improving ease of operation

Inventive Principle:

Principle #25Self-service

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 approach allows for a reliable examination of whether the magnetization directions of the first and second ferromagnetic layers are antiparallel, ensuring proper functioning of the MR element before the orthogonalizing bias function part activates, thereby enhancing the accuracy and reliability of the MR effect.

Implementation Method 1

a first ferromagnetic layer and a second ferromagnetic layer which are exchange-coupled in a manner of making the magnetization directions antiparallel to each other; an orthogonalizing bias function part which is disposed on the rear part of the two free layers and has influence over substantially orthogonalizing the magnetization directions of the two free layers

Methodology Applied

Scientific EffectMagnetoresistance effect: Magnetoresistance

Data Source

PatentUS7615996B1Examination method for CPP-type magnetoresistance effect element having two free layers

Publication Date: 2009.11.10 TDK CORP

AI summary

An examination method is structured, with respect to a magnetization direction of an orthogonalizing bias function part formed on a posterior part of an magnetoresistance (MR) effect element, of changing the magnetization direction of the orthogonalizing bias function part between a first magnetization forming mode, wherein the magnetization direction is from the anterior side of the element to the posterior side thereof, and a second magnetization forming mode, wherein the magnetization direction is from the posterior side of the element to the anterior side thereof, measuring the output waveform of the element in response to an external magnetic field for each magnetization forming mode and checking the state of the output waveforms of both modes in order to examine whether or not the magnetization directions of the first magnetic layer and the second magnetic layer, both of which functions as free layers, are antiparallel to each other in the track width direction before the orthogonalizing bias function part starts functioning. With the structure, it is realized to easily examine whether or not the magnetization directions of two free layers have surely been made antiparallel to each other before operating the orthogonalizing bias function part of an element.