Free Layer Magnetic Read Sensor with Reduced Shield Spacing

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Solution Overview

Problem

Conventional magnetic recording read transducers struggle to effectively read high linear density media due to inadequate performance at reduced shield-to-shield spacing and track width, which is necessary for advancing magnetic recording technology to higher densities.

Innovation Solution

The development of a magnetic read transducer with a 'free layer only' configuration, utilizing a nonmagnetic spacer layer and ferromagnetic free layer, along with side and rear magnetic bias structures, allows for reduced shield-to-shield spacing and enhanced magnetoresistance, enabling improved reading capabilities at higher linear densities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If conventional read sensor configuration is used, then device structure is simple, but shield-to-shield spacing cannot be reduced below 22 nanometers

Engineering Contradiction:

Improveshield-to-shield spacingVSAvoidsensor structure complexity

Core Design Contradiction:

Length of stationary objectVSDevice complexity

Solution Approach 1:

The patent extracts the pinned layer from the traditional GMR sensor configuration, creating a 'free layer only' sensor structure. This removal of the pinned layer eliminates the need for complex antiferromagnetic coupling structures while maintaining sufficient magnetoresistance through the free layer's interaction with the shields, enabling reduced shield-to-shield spacing below 22 nanometers.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the magnetic configuration parameters by using a free layer with specific perpendicular magnetic anisotropy and adjusting the thickness and material composition of the free layer. These parameter changes allow the sensor to achieve adequate magnetoresistance with reduced shield spacing, resolving the contradiction between spacing reduction and performance maintenance.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If shield-to-shield spacing is reduced for higher linear density, then recording density improves, but read sensor performance deteriorates

Engineering Contradiction:

Improvelinear recording densityVSAvoidread sensor performance

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent introduces a nonmagnetic spacer layer as an intermediary between the free layer and the shields. This spacer layer mediates the magnetic interaction, allowing the free layer to effectively sense magnetic fields from high-density media while maintaining structural stability at reduced shield-to-shield spacing, thus preserving read sensor performance despite spacing reduction.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite material structures including the free layer, nonmagnetic spacer layer, and shield layers with specific material compositions. This composite structure optimizes the magnetic and electrical properties, enabling the sensor to maintain high measurement precision even when shield-to-shield spacing is reduced to accommodate higher linear density recording.

Inventive Principle:

Principle #40Composite materials

3Area of stationary object

If track width is reduced for higher density, then areal density improves, but sensor sensitivity decreases

Engineering Contradiction:

Improvetrack widthVSAvoidsensor sensitivity

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality optimization by configuring the free layer with specific magnetic properties and thickness variations across different regions. The free layer's perpendicular magnetic anisotropy and localized magnetic moment orientation enhance sensitivity to narrow track widths, allowing the sensor to maintain measurement precision even when track width is reduced for higher areal density.

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

This configuration enables the magnetic read transducer to effectively read data at higher linear densities by reducing shield-to-shield spacing to less than 15 nanometers, facilitating high linear and areal density magnetic recording applications.

Implementation Method 1

The free layer 28 has a magnetization sensitive to an external magnetic field

Methodology Applied

Scientific EffectMagnetic field sensitivity: Magnetic Field

Implementation Method 2

The read sensor 20 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS10121501B2Free layer magnetic reader that may have a reduced shield-to-shield spacing

Publication Date: 2018.11.06 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A magnetic read apparatus includes a read sensor, a shield structure and a side magnetic bias structure. The read sensor includes a free layer having a side and a nonmagnetic spacer layer. The shield structure includes a shield pinning structure and a shield reference structure. The nonmagnetic spacer layer is between the shield reference structure and the free layer. The shield reference structure is between the shield pinning structure and the nonmagnetic spacer layer. The shield pinning structure includes a pinned magnetic moment in a first direction. The shield reference structure includes a shield reference structure magnetic moment weakly coupled with the pinned magnetic moment. The side magnetic bias structure is adjacent to the side of the free layer.