Read Head Free Layer Biasing for Noise Reduction

Solution Overview

Problem

High aspect ratio read transducers in magnetic data storage devices face challenges with high free layer non-linearity and noise, particularly as they are scaled to fit narrow data tracks, leading to increased magnetic and electronic noise that affects data-reproducing capabilities.

Innovation Solution

A read head design incorporating a free layer biasing structure with side shields that apply a first bias field to the front portion nearest the bearing surface and a second, greater bias field to the rear portion, selectively reducing magnetic noise without impacting readback signal amplitude.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the read transducer is scaled down to fit narrow data tracks for high recording density, then the data-reproducing capability is improved, but magnetic noise and electronic noise increase

Engineering Contradiction:

Improvedata-reproducing capabilityVSAvoidmagnetic noise

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different bias field levels to different regions of the free layer by positioning side shields at specific locations. The first side shield applies a first bias field level to a first region of the free layer, while the second side shield applies a second bias field level to a second region. This local differentiation allows optimization of signal quality in the read region while controlling noise in other regions, resolving the contradiction between maintaining data-reproducing capability and reducing magnetic noise in scaled-down transducers.

Inventive Principle:

Principle #3Local quality

2Productivity

If the read transducer is scaled down to fit narrow data tracks for high recording density, then the data-reproducing capability is improved, but electronic noise increases

Engineering Contradiction:

Improvedata-reproducing capabilityVSAvoidelectronic noise

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different bias field levels to different regions of the free layer by positioning side shields at specific locations. The first side shield applies a first bias field level to a first region of the free layer, while the second side shield applies a second bias field level to a second region. This local differentiation allows optimization of signal quality in the read region while controlling noise in other regions, resolving the contradiction between maintaining data-reproducing capability and reducing electronic noise in scaled-down transducers.

Inventive Principle:

Principle #3Local quality

3Device complexity

If a uniform bias field is applied to the free layer, then the structure is simple, but free layer non-linearity increases

Engineering Contradiction:

Improvebiasing structure complexityVSAvoidfree layer non-linearity

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent employs side shields positioned at specific locations to apply different bias field levels to different regions of the free layer. The first side shield applies a first bias field level to a first region, while the second side shield applies a second bias field level to a second region. This spatial variation in bias field strength compensates for non-linear effects in the free layer, improving magnetic stability and linearity without requiring overly complex biasing structures.

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 approach effectively mitigates magnetic noise in read transducers, maintaining signal quality while accommodating higher recording densities and faster data transfer speeds.

Implementation Method 1

The free layer biasing structure includes at least one side shield that applies a first bias field level to a front portion of the free layer that is nearest to the bearing surface and applies a second bias field level to a rear portion of the free layer that is farthest from the bearing surface

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

The MR sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the adjacent magnetic media

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS9886974B2Read head free layer having front and rear portions biased at different levels

Publication Date: 2018.02.06 SEAGATE TECH LLC

AI summary

A reader having a bearing surface, a free layer, and a free layer biasing structure. The free layer biasing structure includes at least one side shield that applies a first bias field level to a front portion of the free layer that is nearest to the bearing surface and applies a second bias field level to a rear portion of the free layer that is farthest from the bearing surface. The second bias field level is greater than the first bias field level.