Extended Pinned Layer Magnetic Sensor Biasing

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Solution Overview

Problem

The challenge is to develop a magnetic read head that can achieve reduced track width and gap thickness while maintaining magnetic stability and reliability, as existing technologies face limitations in reducing sensor size without compromising pinned layer stability.

Innovation Solution

The magnetic read head incorporates a sensor stack with a magnetic free layer and a pinned layer structure, where the pinned layer is extended in both stripe height and width directions, utilizing soft magnetic bias structures and exchange coupling with antiferromagnetic material to enhance robustness, and the trailing shield is notched to accommodate thicker hard bias layers or replaced with soft bias structures to maintain free layer biasing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the sensor size is reduced to achieve reduced track width and gap thickness, then data density is improved, but pinned layer stability deteriorates

Engineering Contradiction:

Improvedata densityVSAvoidpinned layer stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The pinned layer is extended in the stripe height direction (vertical dimension) beyond the free layer's stripe height, creating an extended pinned layer structure. This dimensional extension provides additional pinning area and improved stability without increasing the lateral footprint, thereby enabling reduced track width while maintaining pinned layer stability

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The trailing shield structure is merged with the extended pinned layer, where the trailing shield is notched to accommodate the extended pinned layer geometry. This integration allows the pinned layer to extend laterally beyond the free layer sides while maintaining structural coherence and magnetic stability

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If the pinned layer is extended in width direction to improve pinning robustness, then pinned layer stability is improved, but free layer biasing becomes more difficult

Engineering Contradiction:

Improvepinned layer stabilityVSAvoidfree layer biasing

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The biasing function is segmented between hard bias structures (for strong pinning) and soft magnetic bias structures (for free layer biasing). The soft magnetic bias structures are positioned laterally outward from the free layer sides and can be exchange coupled with antiferromagnetic material, providing tailored biasing that accommodates the extended pinned layer geometry

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Soft magnetic bias structures serve as intermediary elements between the extended pinned layer and the free layer, providing the necessary magnetic biasing field. These structures can be exchange coupled with antiferromagnetic material to enhance their biasing capability while maintaining compatibility with the extended pinned layer configuration

Inventive Principle:

Principle #24Intermediary (Mediator)

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 allows for improved pinning strength and free layer biasing, ensuring magnetic stability and reliability even at reduced sensor sizes, effectively addressing the limitations of existing technologies.

Implementation Method 1

either or both of the trailing shield and the hard bias structure can be exchange coupled with a layer of antiferromagnetic material to further improve the robustness of the free layer biasing

Methodology Applied

Scientific EffectExchange coupling:

Implementation Method 2

A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field.

Methodology Applied

Scientific EffectGiant magnetoresistive effect: Magnetoresistance

Implementation Method 3

A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media.

Methodology Applied

Scientific EffectTunnel magnetoresistive effect: Magnetoresistance

Implementation Method 4

First and second soft magnetic bias structures extend laterally outward from the first and second sides of the free layer structure

Methodology Applied

Scientific EffectMagnetic biasing: Magnetic Field

Data Source

PatentUS8941954B2Magnetic sensor with extended pinned layer and partial wrap around shield

Publication Date: 2015.01.27 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A magnetic read head that has improved pinned layer stability while also maintaining excellent free layer stability. The free layer has sides that define a trackwidth of the sensor and a back edge that defines a functional stripe height of the sensor. However, the pinned layer can extend significantly beyond both the width of the free layer and the back edge (e.g. stripe height) of the free layer. The sensor also has a soft magnetic bias structure that compensates for the reduced volume presented by the side extension of the pinned layer. The soft magnetic bias structure can be magnetically coupled with the trailing magnetic shield, either parallel coupled or anti-parallel coupled. In addition, all or a portion of the soft magnetic bias structure can be exchange coupled to a layer of anti-ferromagnetic material in order to improve the robustness of the soft magnetic bias structure.