Perpendicular Magnetic Recording Head Bottom Side Shield Design
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Solution Overview
Problem
Perpendicular magnetic recording heads face significant lateral fringing issues, leading to unwanted side-writing and destabilization of magnetic domains, which limits recording area density and increases the risk of overwriting in adjacent tracks.
Innovation Solution
A self-aligned, three-way shielded pole structure is formed using reactive ion etching and ion beam etching techniques, with a combination of tantalum-ruthenium-nickel-chromium or titanium layers, to reduce side fringing while maintaining strong and defined recording flux, allowing for larger pole formation and improved track resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If perpendicular magnetic recording heads are used to achieve high recording area densities, then recording area density is improved, but lateral fringing increases causing unwanted side-writing
Solution Approach 1:
The shield structure is segmented into multiple components: a main pole, a return pole, and multiple side shields (first side shield, second side shield, third side shield) positioned at different locations. This segmentation allows each component to independently manage specific aspects of the magnetic field, with side shields strategically placed to contain lateral fringing while the main pole maintains recording flux.
Solution Approach 2:
Nonmagnetic gaps are introduced as intermediary elements between the main pole and side shields, and between adjacent side shields. These gaps act as mediators that control the magnetic flux distribution, preventing direct magnetic coupling that would cause lateral fringing while maintaining the necessary field strength for recording.
2Object-generated harmful factors
If side shields are added to reduce lateral fringing, then side-writing is reduced, but device complexity increases
Solution Approach 1:
Multiple side shields (first, second, and third side shields) are merged into a coordinated shielding system that works together with the main pole and return pole. The shields are positioned to overlap and cooperate, creating a unified containment structure for lateral fringing without requiring each shield to be independently optimized, thereby reducing overall complexity.
Solution Approach 2:
The shield structure extends into the vertical dimension with side shields positioned at different heights and depths relative to the main pole. This three-dimensional arrangement allows lateral fringing to be contained from multiple spatial perspectives simultaneously, achieving comprehensive side-writing prevention without requiring an overly complex two-dimensional configuration.
3Force
If the pole size is increased to maintain flux strength, then recording flux is improved, but lateral fringing increases causing overwriting
Solution Approach 1:
The magnetic field distribution is optimized with local quality variations: the main pole provides strong concentrated flux for recording, while side shields create localized containment zones at specific positions. The nonmagnetic gaps provide localized field management, allowing strong recording flux where needed while preventing lateral spread in adjacent regions, thus avoiding overwriting.
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 effectively reduces side fringing, enhances flux definition, and prevents overwriting, enabling higher recording area densities up to 500 Gb/in² while maintaining track resolution and flux strength.
Implementation Method 1
A self-aligned, three-way shielded pole structure is formed using reactive ion etching and ion beam etching techniques
Implementation Method 2
A self-aligned, three-way shielded pole structure is formed using reactive ion etching and ion beam etching techniques
Implementation Method 3
perpendicular magnetic recording heads that produce their recording magnetic fields perpendicularly to the recording medium
Implementation Method 4
By means of fringing magnetic fields that extend between two emerging pole pieces, longitudinal recording heads form small magnetic domains within the surface plane of the magnetic medium
Implementation Method 5
A self-aligned, three-way shielded pole structure is formed using reactive ion etching and ion beam etching techniques, with a combination of tantalum-ruthenium-nickel-chromium or titanium layers, to reduce side fringing while maintaining strong and defined recording flux
Data Source
AI summary
A perpendicular magnetic recording (PMR) head has a pole tip shielded laterally by a separated pair of bottom side shields and shielded from above by an upper shield. The bottom side shields surround a lower portion of the pole tip while the upper portion of the pole tip is surrounded by non-magnetic layers. The bottom shields and the non-magnetic layer form a wedge-shaped trench in which the pole tip has been formed by a self-aligned plating process. A write gap layer and an upper shield is formed above the side shields and pole. The resulting structure substantially eliminates track overwrite while maintaining good track definition.