CPP Magnetoresistive Element with Side Shield Layers
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Solution Overview
Problem
Current magnetoresistive effect elements face challenges in achieving ultrahigh recording density due to limitations in narrowing the read gap, insufficient cross-track resolution, and issues with false writing and demagnetization, particularly with the dual free layer structure which struggles to maintain a strong exchange coupling between ferromagnetic layers.
Innovation Solution
A magnetoresistive effect element with a CPP structure, featuring side shield layers that apply a bias magnetic field to incline the magnetization of ferromagnetic layers, allowing for orthogonalization and improved sensitivity, while eliminating the need for an antiferromagnetic layer and synthetic pinned structure, thereby enhancing recording density and reducing false writing risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the read gap is narrowed to increase recording density, then the recording density is improved, but the cross-track resolution deteriorates
Solution Approach 1:
The shield structure is segmented into upper shield layers and side shield layers, with each segment serving a specific function. The upper shield layers narrow the read gap for high recording density, while the side shield layers maintain cross-track resolution by providing lateral magnetic field confinement.
Solution Approach 2:
The invention transitions from a conventional planar shield structure to a three-dimensional shield configuration by adding side shield layers that extend laterally. This dimensional change allows simultaneous optimization of both read gap width and cross-track resolution.
2Device complexity
If the dual free layer structure is used to eliminate antiferromagnetic layers, then the device complexity is reduced, but false writing and demagnetization occur
Solution Approach 1:
Different regions of the ferromagnetic layers are given different magnetic properties through localized exchange coupling. The first ferromagnetic layer has its magnetization direction controlled by exchange coupling with the second ferromagnetic layer, creating local magnetic stability that prevents false writing while maintaining overall structural simplicity.
Solution Approach 2:
Exchange coupling acts as an intermediary mechanism between the two ferromagnetic layers, replacing the need for antiferromagnetic layers. This intermediary coupling maintains reliable magnetization control and prevents false writing without adding structural complexity.
3Productivity
If the element area is reduced to achieve narrower track, then the recording density is improved, but the heat dissipation efficiency deteriorates
Solution Approach 1:
The element structure is segmented into functional regions with optimized current paths. The CPP structure divides current flow into perpendicular paths through the thin film layers, increasing the effective heat dissipation surface area relative to the active sensing area, thereby improving heat dissipation efficiency while maintaining small element footprint.
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 effectively narrows the read gap, improves cross-track resolution, and increases sensitivity to external magnetic fields, addressing the limitations of existing dual free layer structures and enabling better detection and writing accuracy.
Implementation Method 1
the side shield layer is configured to be able to apply a bias magnetic field to at least the first ferromagnetic layer
Implementation Method 2
the second ferromagnetic layer is indirectly magnetically coupled with the lower shield layer via an exchange-coupling functional gap layer positioned between the second ferromagnetic layer and the lower shield layer
Implementation Method 3
each of the upper shield layer and the lower shield layer has an inclined magnetization structure of which its magnetization is inclined relative to the track width direction; the side shield layers are magnetically coupled with the upper shield layer, respectively
Implementation Method 4
a magnetoresistive effect part (MR part), an upper shield layer and a lower shield layer that are lamination-formed so as to interpose the MR part from top and bottom, having a current-perpendicular-to-plane (CPP) structure
Data Source
AI summary
An MR element includes an MR part and upper and lower shield layers in a CPP structure. The MR element has side shield layers so as to interpose the MR part between the side shield layers in a track width direction. The MR part comprises a nonmagnetic intermediate layer and first and second ferromagnetic layers so as to interpose the nonmagnetic intermediate layer between the ferromagnetic layers. Each of the upper and lower shield layers has an inclined magnetization structure such that its magnetization is inclined relative to the track width direction. The side shield layers are magnetically coupled with the upper shield layer, respectively. The second ferromagnetic layer is indirectly magnetically coupled with the lower shield layer via an exchange-coupling functional gap layer. The side shield layer applies a bias magnetic field to the first ferromagnetic layer; and magnetizations of the first and second ferromagnetic layers are substantially orthogonal.