Hybrid Side Shield for PMR Write Head Saturation
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Solution Overview
Problem
Current PMR write heads face challenges in achieving higher tracks per inch (TPI) capability while maintaining low adjacent track interference (ATI) due to side shield tip saturation, which restricts further reduction in side gap dimension for area density improvement.
Innovation Solution
A hybrid side shield design is implemented, comprising a 15-24 kG hot seed layer adjoining the side gap and a 10-19 kG outer layer, with the inner hot seed layer having a higher magnetic saturation value than the outer layer, forming an all-wrap-around shield structure to enhance TPI while maintaining low ATI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the side gap dimension is reduced to achieve higher TPI, then track density improves, but side shield tip saturation occurs which degrades TPI capability
Solution Approach 1:
The side shield is divided into two regions with different magnetic properties: a tip region with high Ms material (15-24 kG) and a body region with low Ms material (10-19 kG). This local differentiation allows the tip to resist saturation at reduced gap dimensions while the body maintains low ATI characteristics.
Solution Approach 2:
The side shield uses a composite structure combining two magnetic materials with different saturation characteristics. The high Ms material at the tip prevents saturation, while the low Ms material in the body reduces far-side ATI, creating a composite shield with optimized overall performance.
2Object-generated harmful factors
If low moment material is used in side shields to reduce far side ATI, then adjacent track interference improves, but side shield tip saturation degrades TPI
Solution Approach 1:
Different regions of the side shield are assigned different magnetic moment characteristics: the tip region uses high moment material to prevent saturation and maintain TPI, while the body region uses low moment material to minimize far-side ATI.
Solution Approach 2:
The side shield is segmented into two distinct magnetic layers: a tip layer with high Ms (15-24 kG) and a body layer with low Ms (10-19 kG). This segmentation allows each region to independently optimize its function without compromising the other.
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 hybrid side shield design effectively minimizes side shield tip saturation, enabling higher TPI and improved area density without increasing adjacent track erasure, thus supporting higher bit density in hard disk drives.
Implementation Method 1
coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through a write pole tip and enters a magnetic medium
Implementation Method 2
a first magnetic layer adjoining the side gap and disposed below the write gap, and a second magnetic layer with a lower magnetization saturation (Ms) than the first magnetic layer
Data Source
AI summary
A perpendicular magnetic recording (PMR) writer is disclosed wherein a hybrid side shield (hSS) has an inner 15-24 kG hot seed layer formed between a gap layer and an outer hSS layer to improve tracks per inch capability while maintaining acceptable adjacent track interference (ATI). The outer hSS layer has a magnetization saturation (Ms) value from 10-19 kG and less than that of the inner hot seed layer. The inner hot seed layer has a far side that is 100 to 500 nm from a center of the main pole and may be coplanar with the sidewalls of an overlying write gap and 19-24 kG trailing shield layer. As a result, the side shield return field is substantially improved over a full side shield made of 12-16 kG material. Meanwhile, the trailing shield return field is substantially the same to enable better area density capability (ADC).