Perpendicular Magnetic Head Shield Protrusion Suppression
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Solution Overview
Problem
Magnetic heads for perpendicular magnetic recording face challenges in accurately defining the throat height and preventing protrusion of the shield layer due to thermal expansion, leading to issues like adjacent track erasing and unwanted writing.
Innovation Solution
A magnetic head design featuring a pole layer and a shield layer with a gap layer in between, where the shield layer incorporates additional nonmagnetic layers to prevent protrusion and ensure accurate throat height definition, using materials with lower thermal expansion coefficients to mitigate heat-induced expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the end face of the shield layer is located forward of the end face of the pole layer to improve linear recording density, then recording density is improved, but the shield layer end portion protrudes due to thermal expansion from coil heat
Solution Approach 1:
A nonmagnetic layer is introduced as an intermediary between the shield layer and the external environment. This nonmagnetic layer has a lower thermal expansion coefficient than the shield layer, acting as a buffer that absorbs thermal expansion differences and prevents the shield layer end portion from protruding while maintaining the forward location of the shield layer end face for high linear recording density
Solution Approach 2:
The thermal expansion coefficient parameter is changed by selecting a nonmagnetic layer material with a lower thermal expansion coefficient than the shield layer material. This parameter change allows the structure to compensate for thermal expansion effects, preventing protrusion while maintaining the desired geometric configuration for high-density recording
2Manufacturing precision
If the track width is reduced to achieve higher recording density, then recording density is improved, but write characteristics such as overwrite property degrade
Solution Approach 1:
The pole layer end face is given an asymmetric shape where the side located backward along the direction of travel is shorter than the opposite side. This local quality modification at the pole layer end face improves write characteristics and overwrite property while maintaining the reduced track width configuration for high recording density
3Manufacturing precision
If the end face of the pole layer is made asymmetric to prevent adjacent track erasing, then write accuracy is improved, but device complexity increases
Solution Approach 1:
The pole layer end face is intentionally designed with an asymmetric shape where one side is shorter than the other. This asymmetry is optimized to prevent adjacent track erasing and unwanted writing while maintaining manufacturability through standard fabrication processes
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 effectively suppresses protrusion of the shield layer and allows for precise definition of the throat height, improving overwrite properties and reducing adjacent track erasing, thereby enhancing recording density and signal fidelity.
Implementation Method 1
a coil for generating a magnetic field corresponding to data to be written on the recording medium
Implementation Method 2
a pole layer having an end face located in the medium facing surface, allowing a magnetic flux corresponding to the field generated by the coil to pass therethrough, and generating a write magnetic field for writing the data on the medium
Implementation Method 3
the shield prevents a magnetic flux from reaching the recording medium, the flux being generated from the end face of the pole layer and extending in directions except the direction orthogonal to the surface of the recording medium
Data Source
AI summary
A magnetic head comprises a pole layer, a shield layer, a gap layer disposed between the pole layer and the shield layer, and a coil. The shield layer incorporates: a first layer disposed on the gap layer; a second layer disposed on the first layer; and a third layer disposed on the second layer. The first layer has an end face located in a medium facing surface. An end face of each of the second and third layers closer to the medium facing surface is located at a distance from the medium facing surface. A first nonmagnetic layer is disposed around the first layer. A second nonmagnetic layer is disposed between the medium facing surface and the end face of the second layer closer to the medium facing surface.