Thin Film Magnetic Head Cap Layer and Bias Structure
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Solution Overview
Problem
The challenge in manufacturing thin film magnetic heads is the insufficient thickness of the cap layer near the GMR or TMR element, leading to leakage of bias magnetic fields and reduced coercive force, which affects reading performance and recording density.
Innovation Solution
A configuration with a pair of magnetic bias layers, a bottom and top magnetic shielding layer, and a second cap layer that extends to the same height as the first cap layers to ensure proper coverage and compatibility, enhancing the coercive force and shielding effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cap layer thickness is reduced to improve manufacturing precision, then the manufacturing precision is improved, but the coercive force decreases and bias magnetic field leakage increases
Solution Approach 1:
The patent applies composite materials by stacking multiple magnetic layers (magnetic pinned layer, magnetic free layer, magnetic bias layer) with different functional properties. The magnetic bias layer with uniaxial magnetic anisotropy compensates for the reduced cap layer thickness, maintaining coercive force while allowing precise thickness control for improved manufacturing precision.
Solution Approach 2:
The magnetic head is segmented into distinct functional layers including the magnetic pinned layer, magnetic free layer, and magnetic bias layer. This segmentation allows each layer to be optimized independently - the cap layer can be made thin for manufacturing precision while the magnetic bias layer provides the necessary coercive force stability.
2Manufacturing precision
If the dimension in read track width direction is reduced to improve recording density, then the recording density is improved, but the magnetic sensitive area narrows and voltage changes decrease in CIP-GMR head
Solution Approach 1:
The patent transitions from CIP-GMR to CPP-GMR configuration, dynamically changing the current flow direction from in-plane to perpendicular-to-plane. This dynamic adjustment allows the read current to pass through the magnetoresistive element in a direction that maintains signal detection capability even when track width is reduced, enabling higher recording density without sacrificing reliability.
3Manufacturing precision
If insulating layers are omitted to reduce linear recording density, then the linear recording density is reduced, but the manufacturing complexity is simplified
Solution Approach 1:
The magnetic bias layer serves multiple functions: it provides the bias magnetic field for the magnetically free layer, acts as a shielding layer, and contributes to the overall magnetic domain control. This multi-functionality eliminates the need for separate insulating layers, reducing linear recording density while maintaining necessary structural complexity for reliable operation.
4Measurement precision
If the thickness of GMR element and magnetic domain controlling layers is reduced to improve read resolution, then the read resolution is improved, but the bias magnetic field leakage increases
Solution Approach 1:
The patent converts the potential harm of reduced layer thickness (which would increase magnetic field leakage) into a benefit by introducing the magnetic bias layer with uniaxial magnetic anisotropy. This layer compensates for the leakage effect, allowing read resolution to be improved through thickness reduction while maintaining bias magnetic field stability.
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 improves the reading performance and stability by maintaining a strong bias magnetic field and reducing external magnetic field interference, enabling higher recording density and smoother surface planarization.
Implementation Method 1
a magnetoresistive element (MR element) exhibiting the magnetoresistive effect (MR effect), is widely used for reading out data written on magnetic recording media
Implementation Method 2
a pair of magnetic bias layers disposed on both sides, in a track-width direction of the magnetic recording medium, of the magnetoresistive element, and applying a bias magnetic field to the magnetoresistive element
Data Source
AI summary
A thin film magnetic head including a magnetoresistive element (MR) having higher reading performance. In manufacturing the thin film magnetic head, after forming an MR element, a pair of magnetic domain controlling layers are formed by stacking a buffer layer, a magnetic bias layer and a first cap layer in this order on both sides, in a track-width direction, of the MR element via an insulating layer, respectively. Then, a second cap layer is formed to cover the upper surface of the MR element and connect the pair of cap-layers. Then, a gap adjustment layer and a top shielding layer are formed to cover the pair of first cap layers and the second cap layer, completing a read head section.