Perpendicular Magnetic Head Pole Shield Gap Optimization

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Solution Overview

Problem

Magnetic heads for perpendicular magnetic recording face challenges in achieving higher recording density while preventing the pole erase phenomenon, where data stored on a recording medium is erased due to residual magnetization of the pole layer, especially when the track width is reduced.

Innovation Solution

A magnetic head design incorporating a shield layer with a specific configuration, where the end face of the shield layer is located forward of the pole layer's end face along the direction of travel, and the neck height (NH) to throat height (TH) ratio (NH/TH) is controlled to be greater than zero and smaller than or equal to 0.5, along with a gap thickness (WG) greater than zero and smaller than or equal to 200 nm, to improve recording density and suppress the pole erase phenomenon.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the track width is reduced to achieve higher recording density, then the linear recording density is improved, but the pole erase phenomenon occurs more frequently due to residual magnetization of the pole layer

Engineering Contradiction:

Improvelinear recording densityVSAvoiddata retention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A gap layer made of nonmagnetic material is introduced between the pole layer and the auxiliary pole/shield layer. This gap layer acts as a magnetic field mediator that prevents direct magnetic coupling, thereby suppressing the pole erase phenomenon caused by residual magnetization while maintaining the reduced track width for high recording density

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent optimizes specific geometric parameters: the gap thickness is controlled at 50-200 nm, and the neck height to throat height ratio (NH/TH) is maintained at 0.2-0.5. These parameter changes create optimal magnetic field distribution that prevents pole erase while achieving high recording density

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the gap thickness between the pole layer and the auxiliary pole is increased to suppress the pole erase phenomenon, then the magnetic coupling is reduced and pole erase is suppressed, but the write characteristics and magnetic field gradient are degraded

Engineering Contradiction:

Improvepole erase suppressionVSAvoidwrite characteristics degradation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The gap thickness is precisely controlled within 50-200 nm, and the NH/TH ratio is optimized at 0.2-0.5. These specific parameter ranges create a balance where the gap is sufficient to reduce residual magnetization effects but not so large as to degrade the write magnetic field gradient and track width definition

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the NH/TH ratio is increased to improve pole erase suppression, then the magnetic coupling control is enhanced, but the write field intensity and magnetic field gradient are reduced

Engineering Contradiction:

Improvepole erase suppressionVSAvoidwrite field intensity

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The NH/TH ratio is optimized at 0.2-0.5, which provides sufficient magnetic coupling control to suppress pole erase while maintaining adequate write field intensity. This specific ratio range balances the competing requirements of pole erase suppression and write field strength

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 configuration enhances recording density and effectively reduces the occurrence of the pole erase phenomenon by optimizing the magnetic coupling between the pole layer and the shield layer, maintaining effective write characteristics and magnetic field gradients.

Implementation Method 1

a coil for generating a magnetic field corresponding to data to be written on the recording medium; a pole layer having an end face located in the medium facing surface, allowing a magnetic flux corresponding to the field generated by the coil to pass therethrough

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the shield layer is capable of making the magnetic field gradient abrupt by taking in the magnetic flux generated from the pole layer

Methodology Applied

Scientific EffectMagnetic flux shielding: Magnetic Field

Data Source

PatentUS7554766B2Magnetic head for perpendicular magnetic recording in which gap thickness and pole layer shape are defined for suppressing occurrence of pole erase phenomenon

Publication Date: 2009.06.30 TDK CORP

AI summary

A magnetic head for perpendicular magnetic recording comprises: a pole layer, a write shield layer, and a gap layer provided between the pole layer and the write shield layer. The pole layer incorporates a track width defining portion and a wide portion. The track width defining portion has an end located in a medium facing surface and defines the track width. The wide portion is coupled to the other end of the track width defining portion and has a width greater than the width of the track width defining portion. The value of NH×TH/WG is greater than zero and smaller than or equal to 0.85 μm, where NH is the distance from the medium facing surface to the boundary between the track width defining portion and the wide portion, WG is the space between the pole layer and the write shield layer taken in the medium facing surface, and TH is the distance from the medium facing surface to a point at which the space between the pole layer and the write shield layer starts to be greater than WG.