Laminate Shield Layers for Thin-Film Magnetic Head External Field Tolerance
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Solution Overview
Problem
Existing thin-film magnetic heads face challenges in tolerating external magnetic fields due to the concentration of magnetic flux near the edges of shield layers, leading to unwanted writing or erasing of data, especially when shield areas are minimized to reduce stray capacitance and improve sensitivity.
Innovation Solution
The implementation of laminate shield layers made of non-magnetic material adjacent to the upper and lower shield layers and auxiliary magnetic pole layers, with edges reaching the head end surface, to effectively couple with and suppress magnetic flux concentration caused by external fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shield areas are minimized to reduce stray capacitance and improve sensitivity, then read output quality is improved, but tolerance to external magnetic fields deteriorates due to magnetic flux concentration near shield edges
Solution Approach 1:
The shield structure is divided into multiple segments: upper shield layer, lower shield layer, and auxiliary magnetic pole layers with distinct functional regions. Each segment is optimized independently - the upper and lower shields are minimized for sensitivity while the auxiliary magnetic pole layers extend to provide external field tolerance through segmented magnetic flux management
Solution Approach 2:
The auxiliary magnetic pole layers act as intermediary elements between the main magnetic pole and the shields. These intermediate layers redirect and distribute magnetic flux away from the shield edges, preventing concentration while maintaining the minimal shield area needed for sensitivity
2Productivity
If shield areas are reduced to minimize stray capacitance, then high-frequency read output is improved, but unwanted writing or erasing increases due to external magnetic field effects
Solution Approach 1:
The minimal shield area that causes harmful external field effects is converted into a benefit by using that same minimal area in conjunction with the auxiliary magnetic pole layers. The reduced shield area minimizes stray capacitance for high-frequency performance while the auxiliary layers compensate for the reduced shielding by actively managing flux distribution
Solution Approach 2:
The magnetic circuit parameters are changed by introducing auxiliary magnetic pole layers with specific magnetic permeability and geometric dimensions. These parameter changes in the auxiliary layers compensate for the reduced shield area, maintaining flux control while preserving high-frequency read output quality
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 configuration enhances the tolerance to external magnetic fields, reducing unwanted writing or erasing and maintaining high-frequency read output quality by minimizing stray capacitance even with smaller shield areas.
Implementation Method 1
a rather large loop of magnetic flux is generated through the soft-magnetic backing layer and the auxiliary magnetic pole. The magnetic flux of the generated loop has a tendency to concentrate near both ends of the edge on the air bearing surface (ABS) side of the auxiliary magnetic pole
Implementation Method 2
at least one laminate shield layer for tolerating an external magnetic field is provided adjacently through a non-magnetic material on one side or on both sides in a track width direction of at least one layer out of the lower shield layer, the upper shield layer and the auxiliary magnetic pole layer
Data Source
AI summary
A thin-film magnetic head having an MR element in which the tolerance of external magnetic field is improved even under the condition that shields have smaller areas. The head includes: an MR element includes lower and upper shield layers provided so as to sandwich an MR multilayer, one of edges of each of the layers reaching a head end surface on an ABS side; and an electromagnetic transducer including main and auxiliary magnetic pole layers, one of edges of each of the layers reaching the head end surface, wherein at least one laminate shield layer for tolerating an external magnetic field is provided adjacently on one side or on both sides in a track width direction of at least one layer out of the upper and lower shield layers and the auxiliary magnetic pole layer, and one edge of the at least one laminate shield layer reaching the head end surface.