Recessed High Moment Wrap-Around Shield for Hard Disk Drive Far Track Interference
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Solution Overview
Problem
Perpendicular magnetic recording systems face challenges with far track interference due to magnetic flux leakage from the write head, leading to data integrity issues in adjacent and distant tracks, despite existing optimizations in main pole design and the use of wrap-around shields.
Innovation Solution
A recessed wrap-around shield with high magnetic moment layers is implemented, where the high-moment portions are tapered away from the air bearing surface or positioned entirely away from it, reducing exposure and flux leakage, thereby minimizing unwanted track erasure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a wrap-around shield with high magnetic moment material is used to reduce magnetic flux leakage, then adjacent track interference is reduced, but far track interference increases due to flux leakage from the wide cross section main pole
Solution Approach 1:
The wrap-around shield is segmented into distinct regions: a first wrap-around shield portion positioned adjacent to the main pole tip with high magnetic moment material, and a second wrap-around shield portion positioned away from the main pole tip with low magnetic moment material. This segmentation allows the high moment portion to capture flux near the pole while the low moment portion prevents flux leakage to far tracks.
Solution Approach 2:
Different portions of the wrap-around shield have different magnetic moment properties tailored to their specific functions. The first portion has high magnetic moment to effectively capture and redirect flux, while the second portion has low magnetic moment to minimize its own flux generation and prevent far track interference. This local differentiation resolves the contradiction between reducing ATI and preventing FTI.
2Power
If the main pole cross section is made wide to increase writing capability, then more magnetic flux is generated, but magnetic leakage increases causing far track interference
Solution Approach 1:
The wrap-around shield acts as an intermediary structure between the wide cross-section main pole and the recording medium. It provides a controlled path for magnetic flux, guiding it through the high moment portion near the pole tip while the low moment portion prevents uncontrolled leakage to far tracks, thus enabling strong writing capability without excessive leakage.
Solution Approach 2:
The magnetic moment parameter of the wrap-around shield is varied spatially along its length. The high magnetic moment region is positioned where flux concentration is needed, while the low magnetic moment region is positioned where flux leakage control is critical. This parameter variation allows the system to achieve both strong writing capability and reduced far track interference.
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
The solution effectively reduces far track interference by minimizing magnetic flux leakage, improving data integrity and reducing the risk of soft errors in hard disk drives, while maintaining the functionality of the magnetic recording field.
Implementation Method 1
magnetic flux leakage from the pole tip can cause ATI and FTI
Implementation Method 2
A perpendicular write head has a main pole with a very small cross section at the pole tip... A strong, highly concentrated magnetic field emits from the writer main pole
Data Source
AI summary
Approaches to improving hard disk drive far track interference problems include utilizing a wrap-around shield having recessed high magnetic moment layer(s). Embodiments include tapering the high-moment portion away from the air bearing surface (ABS) in the cross-track direction away from the write pole, thereby reducing exposure of high moment layers at the ABS to reduce the risk of unwanted track erasure away from the main pole. Embodiments include positioning the high magnetic moment layers in their entirety away from the ABS, such as with a laminate structure of high magnetic moment and low magnetic moment materials laid down in a direction away from the pole tip trailing edge.