PMR Writer Trailing Shield with High Moment Material
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Solution Overview
Problem
Current PMR writers face a tradeoff between trailing shield efficiency and adjacent track interference (ATI) performance, where high magnetization saturation materials improve efficiency but worsen ATI, limiting the achievement of both high area density capability (ADC) and TPI.
Innovation Solution
A novel trailing shield structure with a high moment trailing shield (HMTS) and multiple width and thickness configurations, including a narrow HMTS on a first write gap portion and a wider second write gap portion, combined with different magnetic material layers for the trailing shield, to enhance ADC and ATI while maintaining bits per inch (BPI) performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high magnetization saturation materials are used in the trailing shield, then trailing shield efficiency and ADC are improved, but ATI performance deteriorates
Solution Approach 1:
The trailing shield structure implements local quality by using different magnetic material properties in different regions: a high moment trailing shield (HMTS) with high magnetization saturation (19-24 kG) is placed at the center region directly above the main pole trailing side to maximize trailing shield efficiency and ADC, while lower moment magnetic materials (4-22 kG) are used in the outer regions to minimize field leakage and improve ATI performance. This spatial variation in magnetic material properties resolves the contradiction between trailing shield efficiency and ATI performance.
Solution Approach 2:
The trailing shield employs composite materials by combining multiple magnetic material layers with different magnetization saturation values. The structure includes an inner HMTS layer (19-24 kG) for high efficiency and an outer TS layer (4-22 kG) for low interference, creating a composite magnetic shield that simultaneously achieves both high ADC and low ATI by leveraging the complementary properties of different magnetic materials.
2Reliability
If the trailing shield width is increased, then ADC capability is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The trailing shield is segmented into distinct functional regions: a narrow HMTS region (width w = 10-500 nm) directly above the main pole for high ADC, and wider outer TS regions (width w1 > w) extending to the side shields for structural support and flux management. This segmentation allows each region to be optimized independently, reducing overall device complexity while maintaining high ADC capability through the strategically placed narrow HMTS.
Solution Approach 2:
The patent resolves width-related complexity by transitioning to a multi-dimensional solution: instead of uniformly increasing trailing shield width in two dimensions, the invention varies the width in the cross-track dimension (narrow HMTS at center, wider TS at edges) while maintaining controlled thickness variations in the down-track dimension (first WG portion thickness t1, second WG portion thickness t2). This dimensional differentiation achieves high ADC without proportionally increasing overall device complexity.
3Ease of manufacture
If uniform thickness write gap is used, then manufacturing is simplified, but ATI and TPI performance are compromised
Solution Approach 1:
The write gap structure implements local quality by employing non-uniform thickness distribution: a first WG portion with thickness t1 is positioned above the HMTS region to optimize magnetic flux density for high ADC, while a second WG portion with greater thickness t2 (>t1) extends toward the outer TS regions to reduce field leakage and improve ATI performance. This localized thickness variation is achieved through selective deposition and etching processes that maintain manufacturing feasibility while enhancing 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
The solution improves both area density capability and adjacent track interference performance, achieving better TPI and ADC without compromising BPI, by optimizing the trailing shield design with specific magnetic material properties and configurations.
Implementation Method 1
a HMTS that is made of a magnetic material with a saturation (Bs) value of 19-24 kiloGauss (kG)... a first TS layer made of a material with a Bs less than that of the HMTS... The second TS layer is made of a 16-24 kG material
Implementation Method 2
coils that conduct a current and generate a magnetic flux in the MP layer such that the magnetic flux exits through the MP tip and enters a magnetic medium (disk) adjacent to the ABS
Data Source
AI summary
A PMR writer is disclosed wherein the trailing shield (TS) structure has a high moment trailing shield (HMTS) with a saturation (Bs) from 19 kiloGauss (kG) to 24 kG and a width (w) from 10 nm to 500 nm and is separated from the main pole (MP) trailing side at an air bearing surface (ABS) by a first write gap (WG) portion of thickness t1. A second WG portion of thickness t2 where t2>t1 adjoins the sides of the first WG portion, and has an outer side at a cross-track distance ½ w1 from a center plane that bisects the MP trailing side where w1>w. A first TS layer is formed on the HMTS and on the second WG portion, and has an outer side coplanar with the second WG portion outer side. Accordingly, there is improvement in tracks per inch capability and adjacent track interference.