Coupled Soft Bias Scissor Sensor Hysteresis Reduction
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Solution Overview
Problem
Conventional scissor type magnetoresistive read heads experience bias magnetization reversal and hysteresis due to external stresses, limiting their practical application in magnetic recording systems.
Innovation Solution
A magnetic read head design that includes a soft bias layer directly coupled to the top magnetic shield, eliminating the top insulator layer to enhance magnetic coupling and stability, and adjusting the saturation flux density of the soft bias layer to minimize hysteresis and irreversible switching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a top insulator layer is used to isolate the soft bias layer from the top magnetic shield, then electrical insulation is provided, but magnetic coupling is reduced and stability under external stresses deteriorates
Solution Approach 1:
The top insulator layer is completely removed from the structure. The soft bias layer is directly coupled to the top magnetic shield without any insulating layer between them, eliminating the source of hysteresis and instability while maintaining electrical insulation through alternative design approaches
Solution Approach 2:
The soft bias layer and top magnetic shield are merged into direct contact, eliminating the insulator layer interface. This direct coupling enhances magnetic interaction and stabilizes the magnetization orientation under external stresses, resolving the contradiction between insulation needs and magnetic coupling
2Reliability
If the saturation flux density of the soft bias layer is increased, then magnetic coupling is enhanced, but hysteresis and irreversible switching processes increase
Solution Approach 1:
The saturation flux density of the soft bias layer is optimized to a specific range (1.5T-2.0T) rather than simply increased. This parameter optimization, combined with direct coupling to the top magnetic shield, achieves stable magnetic coupling while minimizing hysteresis and irreversible switching processes
3Measurement precision
If conventional scissor type sensor design is used, then sensitivity is improved, but bias magnetization reversal occurs under external stresses
Solution Approach 1:
The top magnetic shield is given special properties by directly coupling the soft bias layer to it, creating a localized region of enhanced magnetic stability. This local modification stabilizes the magnetization orientation in the critical sensing region without affecting the overall scissor type sensor sensitivity
Solution Approach 2:
The soft bias layer is pre-configured with optimized saturation flux density and directly coupled to the top magnetic shield to create a stabilizing magnetic field before external stresses are applied. This preliminary configuration prevents bias magnetization reversal by establishing a robust magnetic orientation that resists external perturbations
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 design reduces hysteresis and improves magnetic utilization, making the read head more stable and effective under external thermal and electromagnetic stresses, thereby enhancing its practical application.
Implementation Method 1
A soft bias layer is directly coupled to a top magnetic shield of the read sensor
Implementation Method 2
read heads of magnetoresistive devices
Data Source
AI summary
A magnetic read head is provided, comprising a bottom magnetic shield, a first free magnetic layer, a second free magnetic layer, and a top magnetic shield, arranged from bottom to top in this order in a stacking direction from a leading side to a trailing side of the read head. A non-soft bias layer is positioned below the top magnetic shield and on a back side of the first and the second free magnetic layers. The top magnetic shield has a unidirectional anisotropy, the magnetic moments of the top and the bottom magnetic shields are canted relative to a plane of the first and the second free magnetic layers, and the top and the bottom magnetic shields are decoupled from the non-soft bias layer and not magnetically coupled to a soft bias layer.