Thin Film Magnetic Head Shield Bias via Coupling Layer
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Solution Overview
Problem
Conventional thin film magnetic heads face challenges in maintaining a narrow gap between shields while ensuring sufficient bias is applied to the free layer, which affects high-frequency characteristics and recording density.
Innovation Solution
Incorporating an anisotropy providing layer, such as an antiferromagnetic or hard magnetic layer, on the outer side of the shields to magnetically couple with the free layer, reducing the gap between shields and ensuring sufficient bias is applied, thereby improving high-frequency characteristics and recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between shields is increased to accommodate a domain control layer, then the free layer receives sufficient bias magnetic field, but the magnetic field from adjacent bits is more likely to be read, deteriorating high-frequency characteristics
Solution Approach 1:
The patent relocates the anisotropy providing layer from the interior gap between shields to the outer surface of the first shield, changing the spatial dimension of bias application. This allows the free layer to receive sufficient bias magnetic field while maintaining a narrow gap between shields, thereby resolving the contradiction between reliable bias application and precise gap control.
Solution Approach 2:
The patent introduces a magnetic coupling layer as an intermediary between the first shield and the free layer. This intermediary enables magnetic field transmission from the anisotropy providing layer to the free layer through the shield structure, allowing bias application without increasing the shield gap.
2Reliability
If the thickness of the antiferromagnetic layer or hard magnetic layer is increased to provide sufficient bias, then the free layer is adequately biased, but the gap between shields increases, causing high frequency characteristics to deteriorate
Solution Approach 1:
The patent moves the anisotropy providing layer to the outer surface of the first shield, changing the spatial arrangement from thickness-based bias application to surface-based bias application. This allows sufficient bias field generation without increasing the gap between shields, resolving the contradiction between bias strength and gap dimension.
3Manufacturing precision
If the gap between shields is reduced to improve high-frequency characteristics, then adjacent bit interference is reduced, but the free layer does not receive sufficient bias magnetic field
Solution Approach 1:
The patent introduces a magnetic coupling layer as an intermediary that transmits the bias magnetic field from the anisotropy providing layer to the free layer. This intermediary enables effective bias application even when the shield gap is narrow, resolving the contradiction between precise gap control and reliable bias application.
Solution Approach 2:
The patent relocates the anisotropy providing layer to the outer surface of the first shield, creating a new spatial arrangement where bias is applied from the outside rather than through the gap. This dimensional change allows narrow gap configuration while maintaining sufficient bias application to the free layer.
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 the gap between shields, allowing for enhanced high-frequency performance and improved recording density by ensuring sufficient bias is applied to the free layer, addressing the side reading problem and noise suppression.
Implementation Method 1
a magnetic coupling layer that is disposed between the first shield and the free layer and that magnetically couples the first shield with the free layer
Implementation Method 2
an anisotropy providing layer that provides anisotropy to a first shield, which is disposed on a free layer side of the pair of the shields, so that the first shield is magnetized in a desired direction
Implementation Method 3
a magneto resistance effect (MR) film that includes a pinned layer of which a magnetization direction is pinned with respect to an external magnetic field, a free layer of which a magnetization direction varies corresponding to the external magnetic field
Data Source
AI summary
A thin film magnetic head includes; an MR film that includes a pinned layer of which a magnetization direction is pinned, a free layer of which a magnetization direction varies, and a spacer that is disposed therebetween; a pair of shields that are disposed on both sides sandwiching the MR film in a direction orthogonal to a film surface of the MR film; and an anisotropy providing layer that provides anisotropy to a first shield so that the first shield is magnetized in a desired direction, and that is disposed on an opposite side from the MR film with respect to the first shield. The MR film includes a magnetic coupling layer that is disposed between the first shield and the free layer and that magnetically couples the first shield with the free layer.