Magnetic Head Trailing Shield with Gradient Saturation Flux Density
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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 during writing, primarily caused by leakage magnetic fields from non-uniform trailing shields with multiple crystal growth directions and grain boundaries.
Innovation Solution
A magnetic head design featuring a write shield with a trailing shield composed of multiple portions, where the first portion has a higher saturation flux density than the others, and a uniform crystal growth direction is achieved by forming the shield on a flat underlayer, reducing grain boundaries and defects, and incorporating a nonmagnetic gap section between the main pole and the write shield to minimize leakage fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a trailing shield with multiple crystal growth directions is used to increase flexibility in manufacturing, then ease of manufacture is improved, but grain boundaries and defects increase causing unwanted erasure
Solution Approach 1:
The trailing shield is designed with a specific single-crystal orientation (e.g., <100> direction) in the region critical for signal writing, while other regions may have different orientations. This local quality approach ensures that the critical writing region has optimal magnetic properties without requiring the entire shield to be manufactured with the same precision, thus maintaining manufacturing flexibility while improving signal integrity.
Solution Approach 2:
The patent controls the crystal growth direction parameter of the trailing shield material to be uniform in the critical region, rather than allowing multiple orientations. This parameter change from heterogeneous to homogeneous crystal structure reduces grain boundaries and defects, preventing unwanted erasure while still allowing manufacturing through controlled deposition processes.
2Reliability
If a uniform trailing shield structure is used to reduce grain boundaries, then unwanted erasure is prevented, but manufacturing complexity increases
Solution Approach 1:
The trailing shield is segmented into functionally distinct regions: a critical writing region with uniform single-crystal orientation and other regions that may have different structures. This segmentation allows the complex uniform structure to be implemented only where necessary for signal integrity, reducing overall device complexity while maintaining reliability in critical areas.
3Reliability
If the trailing shield is positioned closer to the main pole to reduce leakage fields, then unwanted erasure is reduced, but write magnetic field strength decreases
Solution Approach 1:
The trailing shield employs a local quality approach by implementing uniform single-crystal structure specifically in the region closest to the main pole where leakage field control is critical. This localized structural optimization reduces unwanted erasure in the critical writing region without requiring the entire shield to be repositioned, thereby maintaining write magnetic field strength while improving signal integrity.
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 design enhances write characteristics by maintaining a strong and gradient-rich write magnetic field, preventing unwanted erasure and improving recording density by ensuring smooth magnetization rotation and domain wall displacement within the trailing shield.
Implementation Method 1
The coil produces a magnetic field corresponding to data to be written on the recording medium. The main pole passes a magnetic flux corresponding to the magnetic field produced by the coil, and produces a write magnetic field from its end face.
Implementation Method 2
The trailing shield includes a first portion, a second portion, a third portion and a fourth portion each of which is formed of a magnetic material. The first portion is higher in saturation flux density than the second to fourth portions.
Implementation Method 3
a uniform crystal growth direction is achieved by forming the shield on a flat underlayer, reducing grain boundaries and defects
Implementation Method 4
ensuring smooth magnetization rotation and domain wall displacement within the trailing shield
Implementation Method 5
incorporating a nonmagnetic gap section between the main pole and the write shield to minimize leakage fields
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. The trailing shield includes a first portion, a second portion, a third portion and a fourth portion. The second portion and the third portion are located on opposite sides of the first portion in the track width direction. Top surfaces of the first to third portions are coplanar with each other. The fourth portion lies on the top surfaces of the first to third portions. The first portion is higher in saturation flux density than the second to fourth portions.