Bi-layered Side Shields for Magnetic Read Heads
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Solution Overview
Problem
Current magnetic recording heads face challenges in achieving high cross-track resolution without degrading the readback signal amplitude and signal-to-noise ratio, as increasing side shield saturation magnetization and thickness can reduce the free layer bias and signal quality.
Innovation Solution
The implementation of bi-layered side shields with a main bias layer and a compensation bias layer, where the compensation layer has a lower magnetic moment and opposite magnetization direction, allows for increased side shield magnetic moment and thickness without degrading the readback signal amplitude, by using a spacer layer between the main and compensation bias layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If side shield saturation magnetization and thickness are increased to improve cross-track resolution, then cross-track resolution is improved, but readback signal amplitude and signal-to-noise ratio are degraded
Solution Approach 1:
The side shield is segmented into two distinct layers: a main bias layer with high saturation magnetization for providing strong biasing field, and a compensation layer with lower saturation magnetization for reducing the net magnetic moment. This segmentation allows each layer to perform its specific function optimally without compromising the other.
Solution Approach 2:
Different regions of the side shield structure are assigned different magnetic properties. The main bias layer has high saturation magnetization (Ms1) localized near the free layer to provide strong local biasing, while the compensation layer has lower saturation magnetization (Ms2) to reduce the overall magnetic moment. This local differentiation resolves the contradiction between needing strong local bias and low global moment.
2Measurement precision
If side shield thickness is increased to improve cross-track resolution, then cross-track resolution is improved, but free layer bias is reduced
Solution Approach 1:
The side shield is divided into two functional layers with different thicknesses and magnetic moments. The main bias layer has greater thickness and higher magnetic moment to provide strong biasing force, while the compensation layer has smaller thickness and lower magnetic moment to provide shielding without significantly reducing the bias. This segmentation enables the side shield to simultaneously achieve strong biasing and effective shielding.
Solution Approach 2:
The side shield is constructed as a composite magnetic structure with two layers having different magnetic moment values. This composite structure combines the advantages of high magnetic moment materials (for strong bias) with low magnetic moment materials (for reduced stray field), achieving optimal performance in both biasing and shielding functions.
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 cross-track resolution by improving MT10 and MT50 values without reducing the readback signal amplitude, resulting in better areal density capability and signal-to-noise ratio in magnetic data storage systems.
Implementation Method 1
The side shield includes a main bias layer having a first magnetic moment value and a first magnetization direction and a compensation bias layer having a second magnetic moment value that is less than the first magnetic moment value and a second magnetization direction that is opposite to the first magnetization direction
Data Source
AI summary
A reader includes a free layer and a side shield that biases the free layer. The side shield includes a main bias layer having a first magnetic moment value and a first magnetization direction. The side shield also includes a compensation bias layer having a second magnetic moment value that is less than the first magnetic moment value and a second magnetization direction that is opposite to the first magnetization direction.