Magnetoresistive Sensor AFM-Stabilized Bottom Shield

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Solution Overview

Problem

In magnetic data storage systems, the existing AFM stabilized structures increase shield-to-shield spacing (SSS), leading to higher pulse width at half-height (PW50) and reduced signal-to-noise ratio (SNR), which hinders the achievement of high data densities and sensitive data reading.

Innovation Solution

The introduction of an AFM stabilized bottom shield with a synthetic antiferromagnetic (SAF) structure reduces the SSS by removing the AFM layer from the sensor stack, stabilizing the pinned layer of the bottom shield, and maintaining sensor stability through orthogonal pinning, thereby improving PW50 and SNR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an AFM stabilized structure is used in the sensor stack, then the pinned layer is stabilized, but the shield-to-shield spacing increases leading to reduced signal-to-noise ratio

Engineering Contradiction:

Improvepinned layer stabilityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent divides the AFM stabilization function into two separate components: the bottom shield with SAF structure provides stabilization, while the sensor stack focuses on sensing. This segmentation allows the AFM layer to be removed from the sensor stack, reducing SSS and improving SNR while maintaining pinned layer stability through the bottom shield's SAF structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent moves the AFM stabilization mechanism from the vertical dimension (within the sensor stack) to the horizontal dimension (in the bottom shield structure). By implementing SAF structure in the bottom shield rather than including AFM layers in the sensor stack, the solution resolves the contradiction between stability and measurement precision.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Stability of the object's composition

If AFM layer is included in the sensor stack, then pinned layer stability is achieved, but pulse width at half-height increases reducing data density capability

Engineering Contradiction:

Improvepinned layer stabilityVSAvoiddata density

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent extracts the AFM layer from the sensor stack and relocates the stabilization function to the bottom shield. This extraction reduces the SSS and PW50, enabling higher data densities while the bottom shield's SAF structure maintains the necessary pinned layer stability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the structural parameters of the bottom shield by implementing a SAF structure with specific layer configurations. This parameter change enables the bottom shield to provide AFM-like stabilization without the space requirements, thus reducing PW50 and improving data density capability.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If shield-to-shield spacing is reduced, then data density is improved, but sensor stability against stray fields may be compromised

Engineering Contradiction:

Improvedata densityVSAvoidsensor stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The bottom shield with SAF structure acts as an intermediary that provides magnetic stabilization to the sensor stack. This intermediary structure enables reduced SSS for higher data density while maintaining sensor stability through the bottom shield's magnetic properties and SAF configuration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite material structures in the bottom shield, combining ferromagnetic layers with antiferromagnetic layers in a SAF configuration. This composite structure provides both the magnetic field control needed for stability and the compact form factor required for reduced SSS and higher data density.

Inventive Principle:

Principle #40Composite materials

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 enhances the resolution and stability of the magnetic read/write head, allowing for higher linear and areal data densities while maintaining stability against stray fields, resulting in improved data transfer capabilities.

Implementation Method 1

an antiferromagnetic (AFM) stabilized bottom shield in proximity to the first layer, wherein the AFM stabilized bottom shield is magnetically coupled to the first layer

Methodology Applied

Scientific EffectAntiferromagnetic coupling: Magnetism

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 EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS9251815B2Magnetoresistive sensor with AFM-stabilized bottom shield

Publication Date: 2016.02.02 SEAGATE TECH LLC

AI summary

An apparatus disclosed herein includes a sensor stack including a first layer and an AFM stabilized bottom shield in proximity to the first layer, wherein the AFM stabilized bottom shield is magnetically coupled to the first layer. The apparatus reduces shield-to-shield spacing. The pinned layer of the bottom shield and a pinned layer of the sensor stack are stabilized using the AFM layer in the bottom shield. In one implementation, the bottom shield is made of the SAF structure, with the top layer of the structure adjacent to a pinned layer in the sensor stack.