Magnetoresistive Element Using Spin-Conserving Coupling Layer

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Solution Overview

Problem

Existing magnetoresistive elements face challenges in reducing the read gap length and achieving high sensitivity for magnetic field detection due to the thickness of the antiferromagnetic layer and the limitations of carbon-based structures without an antiferromagnetic layer, which restricts the detectable magnetic field range and sensitivity.

Innovation Solution

A magnetoresistive element with a nonmagnetic conductive coupling layer, potentially made of a carbon material with a graphene structure, that allows electron conduction while conserving spin, coupled between a free ferromagnetic layer and a pinned ferromagnetic layer, with the pinned layer disposed away from the detection surface, enabling reduced read gap length and enhanced sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If a typical MR element configuration with antiferromagnetic layer is used, then the magnetization direction of the pinned layer is fixed, but the read gap length cannot be reduced due to the thickness of the antiferromagnetic layer

Engineering Contradiction:

Improveread gap lengthVSAvoidpositioning precision of pinned layer

Core Design Contradiction:

Length of stationary objectVSManufacturing precision

Solution Approach 1:

The patent removes the antiferromagnetic layer from the conventional MR element structure. Instead of using an antiferromagnetic layer to fix the pinned layer's magnetization direction, the invention employs a spin-dependent scattering mechanism at the interface between the pinned layer and the nonmagnetic conductive layer, eliminating the need for the antiferromagnetic layer and thereby reducing the read gap length.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the mechanism for fixing the pinned layer's magnetization direction from exchange coupling with an antiferromagnetic layer to spin-dependent scattering at a nonmagnetic conductive layer interface. This parameter change in the physical mechanism allows the pinned layer to be positioned closer to the detection surface without compromising its magnetization stability.

Inventive Principle:

Principle #35Parameter changes

2Length of stationary object

If carbon materials with graphene structure are used without antiferromagnetic layer, then read gap length is reduced, but sensitivity and detectable magnetic field range are limited

Engineering Contradiction:

Improveread gap lengthVSAvoidsensitivity of magnetic field detection

Core Design Contradiction:

Length of stationary objectVSMeasurement precision

Solution Approach 1:

The patent employs a composite structure consisting of a pinned layer made of ferromagnetic material and a nonmagnetic conductive layer made of carbon material with graphene structure. This composite structure leverages the spin-dependent scattering properties of the carbon material interface to fix the pinned layer's magnetization direction while maintaining high sensitivity and a wide detectable magnetic field range, overcoming the limitations of using carbon materials alone without an antiferromagnetic layer.

Inventive Principle:

Principle #40Composite materials

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 solution allows for a reduction in read gap length and improved sensitivity by utilizing a nonmagnetic conductive layer to couple the free and pinned layers, enabling effective magnetic field detection with enhanced spin conduction and resistance variation.

Implementation Method 1

a coupling portion made of a nonmagnetic material and coupling the free layer and the pinned layer to each other. The coupling portion includes a nonmagnetic conductive layer that allows electrons to be conducted while conserving their spins.

Methodology Applied

Scientific EffectSpin conduction:

Implementation Method 2

Examples of the MR element include a giant magnetoresistive (GMR) element utilizing a giant magnetoresistive effect

Methodology Applied

Scientific EffectGiant magnetoresistive effect:

Implementation Method 3

and a tunneling magnetoresistive (TMR) element utilizing a tunneling magnetoresistive effect

Methodology Applied

Scientific EffectTunneling magnetoresistive effect:

Implementation Method 4

The antiferromagnetic layer is a layer that fixes the magnetization direction of the pinned layer by means of exchange coupling with the pinned layer

Methodology Applied

Scientific EffectExchange coupling:

Implementation Method 5

The free layer is a ferromagnetic layer whose magnetization direction changes in response to a signal magnetic field

Methodology Applied

Scientific EffectMagnetization response:

Data Source

PatentUS8000065B2Magnetoresistive element and thin-film magnetic head

Publication Date: 2011.08.16 TDK CORP

AI summary

A magnetoresistive element includes: a detection surface that receives a magnetic field to be detected; a free layer made of a ferromagnetic material, having an end face located in the detection surface, and exhibiting a change in magnetization direction in response to the magnetic field to be detected; a pinned layer made of a ferromagnetic material, disposed away from the detection surface, and having a fixed magnetization direction; and a coupling portion made of a nonmagnetic material and coupling the free layer to the pinned layer. The coupling portion includes a nonmagnetic conductive layer that allows electrons to be conducted while conserving their spins.