Perpendicular Magnetic Head Shield Gap Design
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Solution Overview
Problem
Magnetic heads for perpendicular magnetic recording systems face issues with unwanted erasure due to skew, where signals on adjacent tracks are erased or attenuated, leading to reduced recording density and writing capability.
Innovation Solution
The magnetic head design includes a main pole with a width-changing top surface and a write shield with thickness-changing gap sections, which helps in guiding magnetic flux effectively and preventing unwanted erasure by optimizing the write magnetic field strength and gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wrap-around shield is provided to prevent unwanted erasure, then adjacent track erasure is reduced, but writing capability is degraded due to magnetic flux leakage to the shield
Solution Approach 1:
The patent applies local quality by making the gap section thickness non-uniform, specifically thicker at the leading end and thinner at the trailing end. This localized variation in gap thickness allows different regions of the gap section to serve different functions: the thicker leading end prevents flux leakage that would cause adjacent track erasure, while the thinner trailing end maintains strong writing capability by reducing flux leakage to the shield at that location.
Solution Approach 2:
The patent changes the physical parameter of gap section thickness along its length. By varying the thickness parameter from the leading end to the trailing end of the gap section, the patent optimizes the balance between preventing unwanted erasure (requiring thicker gaps) and maintaining writing capability (requiring thinner gaps to minimize flux leakage).
2Reliability
If the main pole end face width decreases with decreasing distance to the top surface, then unwanted erasure is reduced, but writing capability is compromised
Solution Approach 1:
The patent applies local quality by creating a non-uniform width profile of the main pole end face. The width varies in the perpendicular direction to the medium facing surface, with the upper portion having a different width than the lower portion. This allows the upper portion to be narrower for preventing unwanted erasure while the lower portion maintains sufficient width for effective writing capability.
Solution Approach 2:
The patent addresses the contradiction by introducing a new dimension for controlling the main pole geometry - variation in the perpendicular direction to the medium facing surface. This vertical dimensioning allows the main pole end face to have different widths at different heights, enabling simultaneous optimization of both unwanted erasure prevention and writing capability.
3Manufacturing precision
If recording density is enhanced by preventing unwanted erasure, then linear recording density increases, but device complexity increases due to additional shield and gap section structures
Solution Approach 1:
The patent merges the write shield and gap section into an integrated structure where the gap section is formed as part of the write shield assembly. This combining of components reduces the number of separate parts and simplifies manufacturing while still achieving the dual function of preventing unwanted erasure and maintaining writing capability through the optimized gap thickness variation.
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 prevents unwanted erasure while maintaining high writing capability, enhancing recording density and reducing bit error rates by controlling the magnetic field distribution and flux leakage.
Implementation Method 1
a coil for producing a magnetic field corresponding to data to be written on the recording medium, a main pole that passes a magnetic flux corresponding to the magnetic field produced by the coil
Implementation Method 2
a write shield formed of a magnetic material... The write shield includes a trailing shield... a leading shield... and first and second side shields
Data Source
AI summary
A magnetic head includes a main pole, a write shield and a gap section. The write shield includes a trailing shield, a leading shield and two side shields. The gap section includes a trailing gap section, a leading gap section and two side gap sections. Each of the two side gap sections and the leading gap section increases in thickness with increasing distance from a medium facing surface. In the medium facing surface, the thickness of the leading gap section is greater than the width of each of the two side gap sections, and the width of each of the two side gap sections decreases with decreasing distance to the leading gap section.