Recessed Magnetic Shield Design for Far-Field WATE Elimination
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Solution Overview
Problem
Wide area track erasure (WATE) occurs in high-density magnetic recording, where adjacent tracks are inadvertently erased due to fringe fields, posing reliability issues and being economically prohibitive to pre-screen before drive-build.
Innovation Solution
The proximity shield design involves recessing all magnetic shields except the central section a short distance away from the recording medium, reducing accidental erasure by minimizing disturb fields while maintaining side shielding effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If side shields and wrap-around shields are added to shield main writing pole fringing fields, then side shielding ability is improved, but wide area track erasure occurs due to flux concentration at shield edges
Solution Approach 1:
The patent applies local quality by creating a recessed region specifically at the shield edges where flux concentration occurs, while maintaining the original shield structure in the central region. This localized modification targets the specific problem area (edge flux concentration) without altering the overall shielding function, thereby eliminating WATE while preserving side shielding ability.
Solution Approach 2:
The patent introduces a new dimensional feature by recessing the shield edges inward from the air-bearing surface, creating a stepped or tapered profile. This dimensional change moves the shield material away from the recording medium in the critical edge regions, reducing the fringing fields that cause WATE while maintaining shielding coverage.
2Object-generated harmful factors
If shield structure is modified to reduce WATE, then far-field erasure is eliminated, but mechanical strength and adhesion may be compromised
Solution Approach 1:
The patent carefully controls the recess depth parameter, limiting it to a specific range (5-50 nm) that is sufficient to reduce fringing fields and eliminate WATE, while remaining shallow enough to preserve the mechanical integrity and adhesion of the shield structure. This parameter optimization resolves the contradiction between WATE reduction and mechanical strength.
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 effectively eliminates far-field WATE peaks by reducing magnetic interference, enhancing disk drive reliability and preventing unintended data erasure, with the added benefit of increased mechanical strength and adhesion of non-magnetic material.
Implementation Method 1
a side shield (SS) was added... to shield the main writing pole fringing fields... a wrap-around shield (WAS) writer comprising a trailing shield together with side shields
Implementation Method 2
Guan et al. (Headway) show shields having recessed edges to avoid concentration of flux at the edges... Okada et al. describe recessed shields to prevent leaking of the magnetic field
Data Source
AI summary
A shield design for a magnetic write head is described that eliminates the far-field WATE problem while still maintaining side shielding ability. This is achieved by moving all but the central sections of the three shields (LS, SS, and WS) and, optionally, the top yoke a short distance further away from the recording medium than the ABS.