Wrap-around Shielded Writer Homogeneous Material
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Solution Overview
Problem
The existing perpendicular magnetic recording (PMR) write heads face issues due to material and moment mismatches between shield layers, leading to protrusion differences, domain wall formation, and wide area track erasures, which affect recording performance and stability.
Innovation Solution
A wrap-around shielded write head design where all shield layers, including the trailing shield, leading shield, and side shields, are formed from materials with substantially the same composition, hardness, and magnetic moment, ensuring consistent fabrication and performance, with optimized gaps between the main pole and shields to reduce protrusion and domain wall formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different magnetic materials are used for different shield layers to optimize specific performance parameters, then the magnetic performance (field gradient, saturation moment) is improved, but material mismatch causes protrusion differences and domain wall formation at interfaces
Solution Approach 1:
The patent applies homogeneity by using the same magnetic material (e.g., CoFeB or CoFe) for all shield layers including trailing shield, leading shield, and side shields. This eliminates material composition variations and moment mismatches between layers, ensuring uniform protrusion characteristics and preventing domain wall formation at material interfaces while maintaining consistent magnetic performance across all shields
2Force
If high saturation moment material is used in seed layers to improve field gradient, then down-track field gradient is enhanced, but protrusion differences occur due to hardness and lapping rate variations
Solution Approach 1:
The patent uses the same magnetic material composition for both seed layers and shield layers throughout the structure. This eliminates the hardness and lapping rate mismatches that occur when high Bs seed layers are paired with different shield materials, ensuring uniform protrusion while maintaining the beneficial high field gradient properties
Solution Approach 2:
The patent merges the seed layer material with the shield layer material by using identical compositions (e.g., CoFeB for both). This eliminates the interface between dissimilar materials, preventing protrusion differences and domain wall formation while preserving the enhanced field gradient benefits of high saturation moment material
3Ease of manufacture
If low moment material is used in LS and TS shields, then these layers are easier to fabricate, but significant material composition mismatch occurs at ABS interface
Solution Approach 1:
The patent applies homogeneity by using consistent magnetic material composition across all shield layers including LS and TS shields. This eliminates the material composition mismatch at the ABS interface that occurs when low moment materials are used, ensuring uniform protrusion characteristics while maintaining fabrication feasibility
4Reliability
If domain walls form at shield layer interfaces, then material moment mismatches are present, but wide area track erasures occur due to stray fields from magnetic charges
Solution Approach 1:
The patent eliminates domain wall formation by using the same magnetic material for all shield layers, removing the moment mismatches and magnetic charge accumulations at interfaces. This prevents the generation of stray fields that would otherwise cause wide area track erasures, thereby improving recording stability
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 reduces pole tip protrusion, eliminates wide area track erasures, and maintains on-track and off-track performance by using uniform shield materials, improving head-media spacing and field gradients, thereby enhancing recording density and stability.
Implementation Method 1
a perpendicular magnetic recording (PMR) write head whose main pole is surrounded on all sides by shields formed of magnetic material
Implementation Method 2
layers of the same magnetic material
Implementation Method 3
consistent performance can be obtained
Data Source
AI summary
A perpendicular magnetic recording (PMR) head is fabricated with a main pole shielded laterally by a pair of side shields, shielded above by a trailing shield and shielded optionally below by a leading shield. The shields and the seed layers on which they are formed are formed of materials having substantially the same physical characteristics including the same material composition, the same hardness, the same response to processes such as ion beam etching (IBE), chemical mechanical polishing (CMP), mechanical lapping, such as the slider ABS lapping, the same coefficient of thermal expansion (CTE) as well as the same Bs. Optionally, the trailing shield may be formed on a high Bs seed layer to provide the write head with improved down-track performance.