CPP Magnetoresistive Device Shield Domain Control

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Solution Overview

Problem

Current magnetoresistive devices face challenges in stabilizing the domain structure of shield layers, leading to fluctuations in output due to external magnetic fields, which affects the reliability and recording density in high-density magnetic storage systems.

Innovation Solution

A magnetoresistive device with a CPP structure, featuring a nonmagnetic intermediate layer sandwiched between ferromagnetic layers and shield layers configured in a framework shape with a bias magnetic field-applying layer, which efficiently controls the magnetization of the shield layers to maintain a single domain state, reducing output fluctuations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the read gap is narrowed to increase recording density, then the recording density is improved, but the distance between shield layers and free layer decreases causing stronger influence on bias state and worse magnetic field resistance

Engineering Contradiction:

Improverecording densityVSAvoidmagnetic field resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The shield layer is divided into multiple segments (first shield layer, second shield layer, third shield layer) with different functions. The first and second shield layers provide magnetic shielding, while the third shield layer specifically applies bias magnetic field to the free layer, allowing independent optimization of shielding and biasing functions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A nonmagnetic intermediate layer is introduced between the first ferromagnetic layer and the second ferromagnetic layer. This intermediate layer acts as a mediator that prevents direct magnetic interaction between the layers while allowing the bias field from the third shield layer to effectively influence the free layer's magnetization state.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If conventional shield layer configuration is used, then the device structure is simple, but domain structure stability is poor leading to output fluctuations under external magnetic fields

Engineering Contradiction:

Improveshield layer structureVSAvoiddomain structure stability

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the shield structure are assigned different magnetic properties and functions. The first and second shield layers have high permeability for shielding, while the third shield layer is positioned and configured to provide localized bias field to the free layer, creating optimal conditions for domain stability in the read gap region.

Inventive Principle:

Principle #3Local quality

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 enhances the stability of the magnetoresistive device's output by minimizing the impact of external magnetic fields, improving resistance and reliability, and enabling narrower read gaps for higher recording densities.

Implementation Method 1

a bias magnetic field-applying layer, which efficiently controls the magnetization of the shield layers to maintain a single domain state

Methodology Applied

Scientific EffectMagnetization control: Magnetic Field

Implementation Method 2

A magnetoresistive device adapted to read the magnetic field intensity of magnetic recording media or the like as signals

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Data Source

PatentUS8094420B2Magnetoresistive device of the CCP (current perpendicular to plane) type with single-domain control of magnetization, and associated magnetic disk system

Publication Date: 2012.01.10 TDK CORP

AI summary

The invention provides a magnetoresistive device of the CCP (current perpendicular to plane) structure comprising a magnetoresistive unit sandwiched between soft magnetic shield layers with a current applied in the stacking direction. The magnetoresistive unit comprises a nonmagnetic intermediate layer sandwiched between ferromagnetic layers. A planar framework positions the soft magnetic shield layers and comprises a combination of a nonmagnetic gap layer with a bias magnetic field-applying layer constructed by repeating the stacking of a multilayer unit comprising a nonmagnetic underlay layer and a high coercive material layer. The nonmagnetic gap layer is designed and located such that a magnetic flux given out of the bias magnetic field-applying layer is efficiently directed along a closed magnetic path around the framework to form a single domain of magnetization.