TMR Read Head Antiferromagnetic Tabbed Layer Design

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Solution Overview

Problem

Current tunnel magnetoresistance (TMR) read heads in hard disk drives face challenges in further reducing shield-to-shield spacing due to the presence of antiferromagnet (AFM) pinning material, which limits the ability to increase magnetic recording density.

Innovation Solution

The AFM pinning layer is removed from the bottom of the pinned layer and tabbed to either side of the TMR film stack, allowing for ultra-thin shield-to-shield spacing while maintaining strong AFM pinning strength, enabling sub-20 nm thin shield-to-shield spacing for high-density magnetic recording.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the AFM pinning layer is kept underneath the pinned layer, then strong AFM pinning strength is maintained, but the shield-to-shield spacing cannot be reduced further

Engineering Contradiction:

ImproveAFM pinning strengthVSAvoidshield-to-shield spacing

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The AFM pinning layer is segmented into two parts: one portion remains underneath the pinned layer to provide pinning strength, while another portion is extended to the sides (tabbed) to allow reduced shield-to-shield spacing. This segmentation resolves the contradiction by distributing the AFM layer's function across different spatial locations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The AFM pinning layer is extended in the lateral dimension (tabbed to sides) in addition to its traditional position underneath the pinned layer. This dimensional extension allows the shield-to-shield spacing to be reduced while maintaining pinning strength through the combined effect of the underneath and side portions.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If the shield-to-shield spacing is reduced to increase recording density, then magnetic recording density is enhanced, but the AFM pinning strength is compromised

Engineering Contradiction:

Improvemagnetic recording densityVSAvoidAFM pinning strength

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The AFM pinning layer is divided into underneath and side portions, allowing the shield-to-shield spacing to be reduced for higher recording density while the side portions maintain the necessary pinning strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the AFM pinning layer serve different functions: the underneath portion provides localized pinning, while the side portions (tabs) provide additional pinning and allow reduced spacing. This local differentiation resolves the contradiction between density and pinning strength.

Inventive Principle:

Principle #3Local quality

3Length of moving object

If the AFM layer is removed to reduce shield-to-shield spacing, then spacing is reduced, but the read head becomes magnetically bi-directional

Engineering Contradiction:

Improveshield-to-shield spacingVSAvoidmagnetic directionality

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The AFM pinning layer is extracted from its traditional position underneath the pinned layer and repositioned with side extensions. This extraction and repositioning allows the shield-to-shield spacing to be reduced while the side portions of the AFM layer maintain the magnetic directionality that would otherwise be lost.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The AFM layer is extended into the lateral dimension (side tabs) to maintain magnetic directionality while allowing reduced shield-to-shield spacing. This dimensional change enables the read head to remain unidirectional despite the reduced spacing.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 enables the fabrication of read heads with significantly reduced shield-to-shield spacing, enhancing magnetic recording density and facilitating the production of 1 Tb/in² ultra-high density magnetic recording heads.

Implementation Method 1

a pinned layer coupled to an antiferromagnet (AFM) layer

Methodology Applied

Scientific EffectAntiferromagnetism:

Implementation Method 2

AFM pinning strength

Methodology Applied

Scientific EffectExchange coupling:

Implementation Method 3

Current tunnel magnetoresistance (TMR) read heads

Methodology Applied

Scientific EffectTunnel magnetoresistance: Magnetoresistance

Data Source

PatentUS9830936B2Magnetic read head with antiferromagentic layer

Publication Date: 2017.11.28 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A tunnel magnetoresistance (TMR) read sensor having a tabbed AFM layer and an extended pinned layer and methods for making the same are provided. The TMR read sensor has an AFM layer recessed from the air bearing surface, providing a reduced shield-to-shield distance.