High Moment Wrap-Around Shields for Magnetic Read Head Stability
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Solution Overview
Problem
Conventional biasing structures in high-density magnetic recording devices are unable to stabilize sensor elements effectively, leading to instability and reduced resolution as recording density increases, due to randomly distributed hard magnetic grains and lack of improved biasing schemes for ultra-high density recording.
Innovation Solution
A wrap-around shield design with high moment layers and antiferromagnetic coupling is implemented, where side shields and top/bottom shields are formed with high moment materials, providing longitudinal biasing and improved stabilization to the free layer, enhancing micro magnetic read width (uMRW) and cross-track resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hard bias structures are used in high-density recording devices, then the device complexity is reduced, but the sensor stability and resolution deteriorate due to randomly distributed hard magnetic grains
Solution Approach 1:
The patent employs composite magnetic layer structures in the wrap-around shields, combining soft magnetic materials (such as CoFeB, CoFe) with controlled magnetization directions. These composite structures provide stable longitudinal biasing fields without the grain distribution problems of conventional hard bias materials, thereby improving sensor stability while maintaining manageable device complexity through systematic layer design
Solution Approach 2:
The biasing function is segmented into multiple dedicated magnetic layers within the wrap-around shield structure, rather than relying on a single hard bias layer. Each layer (reference layer, free layer, cap layer) performs specific magnetic functions, with the wrap-around shields providing longitudinal biasing through their engineered magnetic moment directions. This segmentation allows independent optimization of each layer's properties to achieve stable biasing
2Quantity of substance
If the sensor element size is decreased to increase recording density, then the recording density improves, but the cross-track resolution deteriorates due to increased edge demagnification
Solution Approach 1:
The wrap-around shields act as counterbalancing magnetic structures that compensate for edge demagnification effects. By positioning magnetic moments in the shields opposite to the demagnetizing fields at the sensor edges, the structure counterweights the demagnetization, maintaining uniform magnetic field distribution and preserving cross-track resolution even as sensor dimensions are reduced for higher density
3Ease of manufacture
If conventional abutting junction configuration is used, then the manufacturing process is simplified, but the junction edge stability deteriorates leading to reduced signal sensitivity
Solution Approach 1:
The patent transitions from conventional planar abutting junctions to a three-dimensional wrap-around shield configuration. The shields extend laterally and vertically to surround the sensor element, providing biasing stabilization from multiple spatial dimensions. This dimensional extension enhances junction edge stability through improved magnetic flux management while remaining compatible with standard thin-film fabrication processes
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 wrap-around shield structure significantly improves the stability and resolution of the sensor, reducing stray magnetic field interference and maintaining high signal sensitivity, thereby achieving better micro magnetic read width sharpness and enhanced cross-track resolution in high-density recording devices.
Implementation Method 1
AFM coupling between a first magnetic layer that is a bottom layer in each side shield stack and a middle magnetic layer in each side shield, and by AFM coupling between the middle magnetic layer and an uppermost third magnetic layer in each side shield
Implementation Method 2
side shields and top/bottom shields are formed with high moment materials, providing longitudinal biasing and improved stabilization to the free layer
Implementation Method 3
In a magnetic recording device in which a read head sensor is based on a spin valve magnetoresistance (SVMR) or a giant magnetoresistance (GMR) effect
Implementation Method 4
In a magnetic recording device in which a read head sensor is based on a spin valve magnetoresistance (SVMR) or a giant magnetoresistance (GMR) effect
Data Source
AI summary
A wrap around shield structure is disclosed for biasing a free layer in a sensor and includes a bottom shield, side shields, and top shield in which each shield element comprises a high moment layer with a magnetization saturation greater than that of Ni70Fe30. The high moment layers provide a better micro read width performance. Side shield structure includes a stack of antiferromagnetically (AFM) coupled magnetic layers on a second high moment layer. A first (lower) magnetic layer in each side shield is ferromagnetically coupled to the second high moment layer, and to a first high moment layer in the bottom shield. A third (upper) magnetic layer in each side shield is ferromagnetically coupled to a third high moment layer in the top shield for improved stabilization. Sensor sidewalls may terminate at a top surface of a reference layer to decrease reader shield spacing.