Perpendicular Magnetic Head Pole Layer Segmentation for Flux Control
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Solution Overview
Problem
In perpendicular magnetic recording systems, achieving high recording density while preventing adjacent track erasing and flux leakage is challenging due to the difficulty in precisely defining the track width and maintaining a strong write magnetic field, especially with smaller neck heights.
Innovation Solution
A magnetic head design featuring a pole layer with a top surface having distinct portions and a nonmagnetic layer between the second portion and the gap layer, which reduces flux leakage and allows for a greater write magnetic field by positioning the pole layer closer to the substrate and using a magnetic shield to control the magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the neck height is reduced to improve overwrite property, then the overwrite capability improves, but the track width definition precision deteriorates
Solution Approach 1:
The pole layer is segmented into a track width defining portion and a wide portion at different heights. The track width defining portion has a smaller height (first height) than the wide portion (second height), allowing the neck height to be reduced for better overwrite property while the wider upper portion maintains precise track width definition through its larger cross-sectional area.
Solution Approach 2:
The pole layer structure transitions from a uniform two-dimensional cross-section to a three-dimensional structure with varying height. By introducing a height dimension variation (first height for track width defining portion, second height for wide portion), the design simultaneously achieves reduced neck height for overwrite improvement and sufficient width for track definition precision.
2Power
If the pole layer is positioned closer to the substrate to enhance write magnetic field, then the write magnetic field strength improves, but flux leakage increases
Solution Approach 1:
A nonmagnetic gap layer is introduced as an intermediary between the pole layer and the shield layer. This gap layer prevents direct magnetic coupling that would cause flux leakage while allowing the pole layer to be positioned close to the substrate for enhanced write magnetic field strength. The gap layer acts as a magnetic insulator that mediates the interaction between the pole layer and shield.
Solution Approach 2:
The magnetic structure is designed with local quality variations where the pole layer has different heights in different regions. The track width defining portion has a smaller height to reduce flux leakage path, while the wide portion has a larger height to maintain strong magnetic field generation, creating localized optimization of magnetic properties.
3Manufacturing precision
If a shield is added to prevent flux expansion and improve recording density, then the recording density improves, but the device complexity increases
Solution Approach 1:
The pole layer is designed to serve multiple functions: it defines the track width through its track width defining portion, generates the write magnetic field through its wide portion, and controls flux distribution through its height variation. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while still improving recording density.
4Manufacturing precision
If the track width defining portion has a uniform width to precisely define track width, then the track width definition precision improves, but the overwrite property deteriorates
Solution Approach 1:
The pole layer is divided into functionally distinct segments: a track width defining portion with uniform width and smaller height for precise track definition, and a wide portion with larger width and height for strong magnetic field generation. This segmentation allows each portion to optimize its function without compromising the other.
Solution Approach 2:
Instead of varying the width of the track width defining portion (which would compromise track definition precision), the design varies the height dimension. The track width defining portion has a first height while the wide portion has a second height greater than the first, allowing overwrite property improvement through height variation while maintaining uniform width for precise track definition.
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 design enables precise definition of the track width and enhances the write magnetic field strength, reducing adjacent track erasing and flux leakage, thereby improving recording density and write characteristics.
Implementation Method 1
a coil for generating a magnetic field corresponding to data to be written on a recording medium
Implementation Method 2
a pole layer for allowing a magnetic flux corresponding to the magnetic field generated by the coil to pass therethrough and generating a write magnetic field for writing the data on the recording medium
Implementation Method 3
The shield has a function of preventing a magnetic flux from reaching the recording medium, the flux having been generated from the end face of the pole layer and expanding in directions except the direction orthogonal to the surface of the recording medium
Data Source
AI summary
A magnetic head includes: a coil; a pole layer; a shield having an end face located in a medium facing surface forward of an end face of the pole layer along a direction of travel of a recording medium; a gap layer between the shield and the pole layer; and a substrate on which the foregoing elements are stacked. The top surface of the pole layer includes: first and second portions with a difference in height therebetween; and a third portion connecting the first and second portions to each other. The first portion has an edge located in the medium facing surface, and the second portion is located farther from the medium facing surface and from the substrate than the first portion. The magnetic head further includes a nonmagnetic layer disposed between the second portion and the gap layer. The nonmagnetic layer has a surface touching the second portion, the surface having an edge located at the boundary between the second and third portions. The nonmagnetic layer has a thickness equal to or greater than the difference in height between the first and second portions.