Magnetic Sensor Barrier Layer Contacting Shield

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Solution Overview

Problem

The existing magnetic read/write head designs with antiferromagnetic (AFM) and synthetic antiferromagnet (SAF) layers face challenges in achieving lower shield-to-shield spacing (SSS) due to edge domain formation, which affects signal-to-noise ratio (SNR) and data density, limiting the sensitivity and resolution of magnetic data storage systems.

Innovation Solution

The design removes the AFM and SAF layers and introduces a barrier layer in direct contact with the bottom shield of the magnetoresistive (MR) sensor stack, allowing the free layer to rotate freely and reducing SSS, thereby enhancing the signal-to-noise ratio and cross-track resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If AFM and SAF layers are used in the sensor stack, then the sensor stability is improved, but the shield-to-shield spacing increases

Engineering Contradiction:

Improvesensor stabilityVSAvoidshield-to-shield spacing

Core Design Contradiction:

Stability of the object's compositionVSLength of stationary object

Solution Approach 1:

The patent removes the AFM and SAF layers from the sensor stack, extracting the components that were causing edge domain formation and excessive SSS. This extraction allows the free layer to rotate freely without the stabilizing constraint of AFM/SAF layers, directly reducing the shield-to-shield spacing while managing edge domain issues through alternative means.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a barrier layer as an intermediary component between the free layer and the bottom shield. This barrier layer serves as a mediator that prevents direct contact between the free layer and shield, thereby suppressing edge domain formation without requiring the bulky AFM/SAF stabilization structure, achieving both reduced SSS and maintained sensor stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If barrier layer is added between free layer and bottom shield, then edge domain formation is reduced, but device complexity increases

Engineering Contradiction:

Improveedge domain formationVSAvoiddevice complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts the complex AFM and SAF stabilization layers from the sensor stack and replaces them with a simpler barrier layer configuration. This extraction simplifies the overall device structure by removing multiple functional layers and replacing them with a single barrier layer that performs the essential function of preventing edge domain formation.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the structural parameters of the sensor stack by introducing the barrier layer with specific thickness and material properties. This parameter change allows the free layer to rotate freely while preventing direct contact with the bottom shield, thereby reducing edge domain formation without requiring complex multi-layer stabilization structures.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If shield-to-shield spacing is reduced, then data density is improved, but signal-to-noise ratio deteriorates

Engineering Contradiction:

Improvedata densityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The barrier layer acts as an intermediary that enables reduced SSS while maintaining acceptable SNR by preventing edge domain formation at the free layer-shield interface. This mediator allows the system to achieve higher data density through reduced spacing without the penalty of excessive noise from edge domains.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent optimizes the barrier layer thickness and material properties to achieve the right balance between reducing SSS for higher data density and maintaining SNR by suppressing edge domain formation. The specific parameter choices for the barrier layer enable simultaneous improvement in data density while managing noise levels.

Inventive Principle:

Principle #35Parameter changes

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 configuration reduces pulse width fluctuations (PW50) and increases the signal-to-noise ratio, enabling higher linear data density and improved areal density in magnetic data storage systems by minimizing SSS and stabilizing the sensor against edge domain formation.

Implementation Method 1

stabilizing the sensor against edge domain formation

Methodology Applied

Scientific EffectEdge domain formation suppression:

Implementation Method 2

Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Data Source

PatentUS9478239B2Reader structure with barrier layer contacting shield

Publication Date: 2016.10.25 SEAGATE TECH LLC

AI summary

Implementations disclosed herein include a reader comprising a magnetically free layer and first barrier layer, wherein the barrier layer is in direct contact with a bottom shield in a down-track direction. Another implementation includes a device comprising a sensor stack comprising a free layer and a barrier layer; a synthetic antiferromagnetic shield layer comprising a reference layer and a pinned layer, wherein direction of magnetization of the reference layer forms an obtuse angle with direction of magnetization of the free layer in a quiescent state.