Patterned High Moment Trailing Shield for PMR Write Head
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Solution Overview
Problem
Current perpendicular magnetic recording (PMR) writer designs face limitations in achieving higher bits per inch (BPI) and tracks per inch (TPI) while maintaining or improving adjacent track interference (ATI), due to the uniform down-track thickness of the high moment trailing shield (HMTS) which restricts the tradeoff between down-track and cross-track performance.
Innovation Solution
A patterned HMTS layer with varying down-track thickness as a function of cross-track position, featuring a larger thickness and smaller gap at off-track center regions and a smaller thickness and larger gap at center track positions, optimized for better overwrite performance and BPI capability within an all wrap around shield structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the HMTS has uniform down-track thickness, then the manufacturing is simplified, but the ability to optimize both down-track performance (BPI) and cross-track performance (TPI and ATI) is limited
Solution Approach 1:
The HMTS is designed with spatially varying down-track thickness: thicker at off-track center regions and thinner at center track positions. This local differentiation allows the shield to provide enhanced field gradient at off-track regions for improved TPI and ATI, while maintaining adequate shielding at the center track for optimal BPI performance.
Solution Approach 2:
The invention transitions from a uniform one-dimensional HMTS design to a two-dimensional thickness profile that varies in the cross-track direction. This dimensional change enables independent optimization of magnetic field characteristics at different lateral positions, resolving the tradeoff between down-track and cross-track performance.
2Manufacturing precision
If the HMTS thickness is increased, then the trailing shield return field is enhanced for better BPI, but the adjacent track interference increases
Solution Approach 1:
The HMTS thickness is locally optimized: thicker regions at off-track positions provide enhanced field gradient to reduce ATI, while thinner regions at center track positions maintain adequate shielding without excessive interference. This spatial differentiation resolves the contradiction between improving BPI and reducing ATI.
3Object-generated harmful factors
If the HMTS thickness is decreased, then the adjacent track interference is reduced, but the trailing shield return field is weakened compromising BPI
Solution Approach 1:
The HMTS is designed with position-dependent thickness: thinner at center track positions to reduce ATI while maintaining adequate return field, and thicker at off-track regions to enhance field gradient for improved TPI and ATI without compromising center track performance.
4Manufacturing precision
If the gap between HMTS and main pole is reduced, then the flux shunting is improved for better TPI, but the down-track field gradient is reduced affecting BPI
Solution Approach 1:
The gap between HMTS and main pole is locally varied: smaller gap at off-track regions enhances flux shunting for improved TPI, while larger gap at center track positions maintains down-track field gradient for optimal BPI performance.
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
Enhances BPI and overwrite performance without compromising TPI and ATI, by providing a substantial trailing shield return field at the center track and shunting excessive magnetic flux at off-track regions, thus improving writing quality and storage area density.
Implementation Method 1
The HMTS attracts more main pole (MP) field to return from the soft underlayer (SUL) and thus enhance the field gradient in the down-track direction
Implementation Method 2
The spacing (gap) between the HMTS and MP also controls the flux shunting of MP field and helps protect TPI and ATI
Data Source
AI summary
A perpendicular magnetic recording writer is disclosed wherein a first trailing shield (HMTS) layer has a down-track (DT) thickness d in portions thereof proximate to a center plane that bisects the main pole tip trailing side to enable enhanced trailing shield return field at track center thereby improving bits per inch (BPI) capability. Meanwhile, at off track center positions, that in some embodiments are from 25 nm to 500 nm from the center plane, the HMTS layer has a DT thickness d1, where d1>d, and a smaller dielectric gap between the HMTS layer and the main pole thereby protecting side shield return field and adjacent track interference (ATI) performance. A method of forming the HMTS layer on a write gap is provided and includes patterning the HMTS layer in a back portion to form openings that are filled with the smaller dielectric gap and HTMS layer thickness d1.