Magnetoresistive Sensor Shield with Variable Permeability

Solution Overview

Problem

Magnetic read/write heads with smaller magnetoresistive (MR) sensors face challenges in reducing magnetic noise and maintaining signal amplitude due to increased areal recording densities, requiring a balance between shield permeability for pulse slimming and stability.

Innovation Solution

A sensor apparatus with a sensor stack within a shielding structure featuring locally enhanced permeability regions near the sensor stack, achieved by biasing the magnetic orientation of shield elements antiparallel to the rest of the shielding structure, creating regions of decreased anisotropy and increased permeability proximal to the sensor stack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If shield permeability is increased to reduce pulse width and improve signal resolution, then signal resolution is improved, but shield stability deteriorates

Engineering Contradiction:

Improvesignal resolutionVSAvoidshield stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by creating regions of high permeability specifically at the shield edges adjacent to the sensor stack, while the bulk shield material maintains lower permeability for stability. This is achieved through localized magnetic biasing structures that enhance permeability only where needed for pulse slimming, rather than uniformly across the entire shield.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the magnetic permeability parameter of the shield by applying magnetic biasing fields that rotate the magnetization of shield regions. This allows dynamic control of permeability - increasing it locally at shield edges to reduce pulse width while maintaining overall shield stability through controlled parameter modification.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If MR sensors are made smaller to accommodate higher areal recording densities, then storage capacity is improved, but magnetic noise increases

Engineering Contradiction:

Improveareal recording densityVSAvoidmagnetic noise

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating regions of high permeability specifically at the shield edges adjacent to the sensor stack, while the bulk shield material maintains lower permeability for stability. This is achieved through localized magnetic biasing structures that enhance permeability only where needed for pulse slimming, rather than uniformly across the entire shield.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the magnetic permeability parameter of the shield by applying magnetic biasing fields that rotate the magnetization of shield regions. This allows dynamic control of permeability - increasing it locally at shield edges to reduce pulse width while maintaining overall shield stability through controlled parameter modification.

Inventive Principle:

Principle #35Parameter changes

3Length of moving object

If shield permeability is increased to reduce pulse width, then pulse width is reduced, but magnetic interference from external fields increases

Engineering Contradiction:

Improvepulse widthVSAvoidmagnetic interference

Core Design Contradiction:

Length of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by creating regions of high permeability specifically at the shield edges adjacent to the sensor stack, while the bulk shield material maintains lower permeability for stability. This is achieved through localized magnetic biasing structures that enhance permeability only where needed for pulse slimming, rather than uniformly across the entire shield.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the magnetic permeability parameter of the shield by applying magnetic biasing fields that rotate the magnetization of shield regions. This allows dynamic control of permeability - increasing it locally at shield edges to reduce pulse width while maintaining overall shield stability through controlled parameter modification.

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 approach enhances signal resolution by reducing pulse width (PW50) while maintaining shield stability, improving the signal-to-noise ratio (SNR) and reducing incidental magnetic interference.

Implementation Method 1

a first region of the shielding structure with a permeability that is greater than a permeability of a second region of the shielding structure

Methodology Applied

Scientific EffectMagnetic shielding: Magnetic Field

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

PatentUS9019664B2Magnetoresistive sensor with variable shield permeability

Publication Date: 2015.04.28 SEAGATE TECH LLC

AI summary

Implementations disclosed herein allow a signal detected by a magnetoresistive (MR) sensor to be improved by providing for one or more regions of reduced anisotropy proximal to a sensor stack within a shielding structure.