Wide Seed Layer Stack for Magnetic Read Head Resolution
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Solution Overview
Problem
In magnetic data storage systems, the shield-to-shield spacing (SSS) in magnetic read/write heads is too large, leading to increased pulse width fluctuations and reduced signal-to-noise ratio, which limits data density and cross-track resolution.
Innovation Solution
A sensor stack with a synthetic antiferromagnetic (SAF)/antiferromagnetic (AFM) structure having a wide areal extent relative to the free layer, where the cross-track width of the seed layer is greater than that of the free layer, and the SAF/AFM width is congruent with or larger than the combined width of the free layer and permanent magnets, reducing SSS and improving stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the shield-to-shield spacing is reduced to improve cross-track resolution and linear density, then pulse width decreases and areal density increases, but the sensor stack becomes more complex and manufacturing becomes more difficult
Solution Approach 1:
The seed layer structure is segmented into multiple parts with different cross-track widths. The first part has a wider width that extends beyond the free layer, while the second part has a narrower width aligned with the free layer. This segmentation allows the wider seed layer to provide enhanced stability and reduced pulse width fluctuations, while the narrower portion maintains compatibility with the free layer dimensions, thus improving cross-track resolution without excessive complexity
Solution Approach 2:
Different regions of the seed layer are given different widths to serve different functions. The wider first part provides enhanced magnetic stability and reduced pulse width, while the narrower second part maintains alignment with the free layer for optimal signal detection. This local differentiation of properties allows the structure to simultaneously achieve reduced SSS and improved manufacturing feasibility
2Stability of the object's composition
If the seed layer cross-track width is increased to improve stability and reduce pulse width, then linear density and areal density increase, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The seed layer is divided into two parts with distinct widths: a wider first part for enhanced magnetic stability and a narrower second part for manufacturing compatibility. This segmentation enables the wider portion to reduce pulse width fluctuations and improve linear density, while the narrower portion maintains ease of fabrication and alignment with the free layer
Solution Approach 2:
The cross-track width parameter of the seed layer is changed in a specific pattern - wider in the first part and narrower in the second part. This parameter variation optimizes the magnetic stability and reduces pulse width while maintaining manufacturability, as the narrower second part can be more easily fabricated and aligned with the free layer
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 decreases pulse width, enhances linear density, and improves areal density and cross-track resolution by reducing noise and stabilizing the sensor, thereby increasing the signal-to-noise ratio.
Implementation Method 1
an antiferromagnetic (AFM) seed layer, a synthetic antiferromagnetic (SAF) layer
Implementation Method 2
The second soft layer rotates freely in response to an external field and is called the 'free layer (FL)'
Implementation Method 3
a magnetoresistive (MR) sensor for retrieving magnetically encoded information stored on a magnetic disc. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor
Data Source
AI summary
A stack having a seed layer structure with a first part having a first cross-track width and a free layer deposited over the seed layer structure and with a second cross-track width, wherein the first cross-track width is greater than the second cross-track width. In one implementation, the seed layer structure further comprises an antiferromagnetic (AFM) layer and a synthetic antiferromagnetic (SAF) layer. In one alternate implementation, the cross-track width of the seed layer structure is substantially equal to the combined cross-track width of the free layer and cross-track width of two permanent magnets.