Magnetic Sensor Free Layer Stripe Height Segmentation
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Solution Overview
Problem
Dual free layer sensing laminations in data storage devices often experience unstable local magnetizations and increased noise due to inadvertent coupling, leading to degraded data sensing performance and higher error rates.
Innovation Solution
A magnetically responsive stack with first and second free layers of differing stripe heights and square rear surfaces, configured without a fixed magnetization, where the stripe heights and biasing magnet position are tuned to minimize coupling and stabilize the free layers, allowing for consistent and strong data signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If dual free layer sensing lamination is used to reduce physical size and magnetic size of transducing element, then device miniaturization is achieved, but inadvertent coupling between free layers occurs leading to unstable local magnetizations and increased noise
Solution Approach 1:
The sensing lamination is segmented into multiple free layers (first free layer and second free layer) with different stripe heights. This segmentation allows each layer to be independently controlled and positioned, enabling the top free layer to sense data bits while the bottom free layer is positioned to reduce inadvertent coupling, thus maintaining stability while achieving miniaturization.
Solution Approach 2:
Different portions of the sensing lamination are given different local properties through varying stripe heights. The top free layer has a greater stripe height optimized for sensing, while the bottom free layer has a reduced stripe height that minimizes coupling and noise. This local differentiation resolves the contradiction by allowing miniaturization without compromising stability.
2Reliability
If free layer thickness is reduced to decrease coupling, then noise is reduced, but signal amplitude is degraded
Solution Approach 1:
The patent applies different stripe heights to different free layers to optimize their respective functions. The top free layer maintains sufficient thickness for strong signal generation, while the bottom free layer uses reduced thickness to minimize coupling and noise. This local quality differentiation resolves the contradiction between noise reduction and signal preservation.
Solution Approach 2:
Instead of uniformly reducing thickness in one dimension, the patent introduces vertical dimensionality variation through different stripe heights. This allows the system to reduce coupling (noise) in the bottom layer while preserving signal amplitude in the top layer, effectively resolving the contradiction through dimensional differentiation.
3Ease of manufacture
If uniform stripe height is used in dual free layer structure, then fabrication is simplified, but coupling between layers cannot be reduced
Solution Approach 1:
The uniform structure is segmented into regions with different stripe heights. This segmentation can be achieved through selective etching or deposition processes that are extensions of standard fabrication techniques, thereby reducing coupling without fundamentally complicating the manufacturing process.
Solution Approach 2:
The patent incorporates stripe height differentiation into the initial fabrication process through preliminary patterning or selective deposition. By establishing the different heights during manufacturing rather than requiring post-processing, the solution maintains ease of manufacture while achieving the desired coupling reduction.
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 reduces noise and preserves signal amplitude by isolating free layer coupling proximal the air bearing surface, resulting in improved data reading accuracy and reduced error rates, while maintaining a reduced physical and magnetic size of the transducing element.
Implementation Method 1
magnetic sensor capable of distinguishing between data bits
Data Source
AI summary
A magnetic sensor may be generally configured in accordance with various embodiments to have a magnetically responsive stack with first and second free layers and without a fixed magnetization. The first and second free layers can be tuned to have different stripe heights from an air bearing surface (ABS) and square rear surface features distal the ABS.