Perpendicular Magnetic Head Shield Segmentation for Throat Height Control
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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 with overwrite property and signal-to-noise ratio.
Innovation Solution
A magnetic head design featuring a pole layer and shield layer with a gap layer in between, where nonmagnetic layers are used to control the throat height and prevent shield layer protrusion, utilizing a specific structure and manufacturing process to ensure accurate throat height definition and improved magnetic flux management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the shield layer is made thinner to reduce the throat height, then the linear recording density is improved, but the shield layer protrudes due to thermal expansion from the coil, degrading the overwrite property and signal-to-noise ratio
Solution Approach 1:
The shield layer is divided into multiple segments (first shield layer, second shield layer, third shield layer) with different thicknesses and positions. The first shield layer has a thinner portion facing the pole layer to reduce throat height, while the second and third shield layers provide additional support and coverage to prevent protrusion, thus resolving the contradiction between reducing throat height and preventing thermal expansion issues.
Solution Approach 2:
Different portions of the shield layer are given different thicknesses and material properties. The first shield layer has a thinner portion at the throat region to improve recording density, while other portions maintain sufficient thickness to prevent protrusion. Nonmagnetic layers are selectively placed in specific regions to control thermal expansion locally without affecting the overall shield function.
2Ease of operation
If the throat height is reduced to improve overwrite property, then the write characteristics are improved, but the shield layer protrusion occurs due to thermal expansion, degrading the signal-to-noise ratio
Solution Approach 1:
The shield layer is segmented into multiple layers with different functions. The first shield layer is positioned to define the throat height for good overwrite property, while the second and third shield layers are positioned to prevent protrusion and maintain signal integrity, thus resolving the contradiction between overwrite property and signal-to-noise ratio.
Solution Approach 2:
Nonmagnetic layers are introduced as intermediary elements between the coil and the shield layer. These nonmagnetic layers act as thermal barriers and structural supports that prevent the shield layer from protruding due to thermal expansion from the coil, thereby maintaining both good overwrite property and high signal-to-noise ratio.
3Device complexity
If a single-layer shield structure is used to simplify the device, then the manufacturing process is simpler, but the throat height cannot be defined accurately and shield layer protrusion occurs
Solution Approach 1:
The shield layer is divided into multiple segments (first, second, and third shield layers) that can be manufactured separately with precise thickness control and then assembled. This segmentation allows each layer to be optimized for specific functions (throat height definition, thermal expansion compensation, and structural support), achieving high manufacturing precision while maintaining reasonable device complexity.
Solution Approach 2:
The invention changes the parameters of the shield layer structure by introducing multiple layers with different thicknesses, materials, and positions. This allows precise control of the throat height parameter while compensating for thermal expansion effects, achieving accurate manufacturing precision without excessive device complexity.
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 enables precise definition of the throat height and suppression of shield layer protrusion, enhancing overwrite property and signal-to-noise ratio, thereby improving recording density and reducing unwanted data erasure.
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
Implementation Method 3
The shield also has a function of returning a magnetic flux that has been generated from the end face of the pole layer and has magnetized 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, a second layer, a third layer and a fourth layer that are disposed on the gap layer one by one. The first layer has an end face located in a medium facing surface. The second layer has: a first surface located in the medium facing surface; a second surface touching the first layer; and a third surface opposite to the second surface. The third layer touches the third surface of the second layer. An end face of each of the third and fourth layers closer to the medium facing surface is located at a distance from the medium facing surface.