Trapezoidal Reader Shape for SNR Improvement
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Solution Overview
Problem
Modern data storage devices face challenges with low signal-to-noise ratio (SNR) due to low reader widths, recessed antiferromagnetic layers, and heat-assisted magnetic recording, which impede further advancements in areal density increases.
Innovation Solution
The design of a non-rectangular recording head with a trapezoidal shape and bias elements that shift shape anisotropy in cross-track and downtrack directions, increasing reader volume and area, and using side bias elements to reduce magnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the reader width is reduced to increase areal density, then the storage capacity increases, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The reader is designed with a non-rectangular, trapezoidal shape where the width varies along the length. The front-end width (at the bearing surface) is smaller than the average width, creating an asymmetric geometry that increases the reader volume and area without compromising the cross-track performance at the critical bearing surface location. This asymmetric design allows more magnetic material to be included in the reader structure, improving the signal-to-noise ratio while maintaining the required areal density.
2Reliability
If the reader volume is increased to improve signal-to-noise ratio, then the magnetic noise averaging improves, but the cross-track performance may be impacted
Solution Approach 1:
The reader geometry is optimized with different widths at different locations along its length. The front-end portion (at the bearing surface) maintains a smaller width to preserve cross-track performance and resolution, while the rear-end portion has a larger width to increase the overall reader volume and area for better signal-to-noise ratio. This local differentiation of dimensions allows each region of the reader to fulfill its specific function optimally.
3Reliability
If bias elements are added to suppress magnetic noise, then the signal-to-noise ratio improves, but the device complexity increases
Solution Approach 1:
The bias elements are positioned proximate to the sides of the reader and utilize the reader's own geometric shape and magnetic properties to generate the necessary bias field. The non-rectangular geometry itself contributes to the magnetic anisotropy and biasing, reducing the need for additional complex biasing structures. This self-service approach allows the reader structure to partially provide its own biasing function, reducing overall device complexity.
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 approach enhances the signal-to-noise ratio by reducing reader resistance, averaging magnetic noise, and suppressing noise through shape anisotropy, resulting in improved data reading capabilities without negatively impacting cross-track performance.
Implementation Method 1
bias elements that shift shape anisotropy in cross-track and downtrack directions, increasing reader volume and area, and using side bias elements to reduce magnetic noise
Implementation Method 2
using side bias elements to reduce magnetic noise
Implementation Method 3
enhances the signal-to-noise ratio by reducing reader resistance
Data Source
AI summary
A recording head that includes a reader having a front end at a bearing surface of the recording head and a rear end behind the bearing surface. The reader has a non-rectangular shape with a front-end width that is less than an average width of the reader. A first bias element is positioned proximate to a first side of the reader, and a second bias element is positioned proximate to a second side of the reader. Each of the first and second bias elements has a bias level that is a function of a ratio of the front-end width to the average width of the reader.