PMR Writer Main Pole Shape Control via Shallower Side Shield Angles
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Solution Overview
Problem
Current perpendicular magnetic recording (PMR) writers face challenges in achieving reproducible performance due to non-uniform film roughness of magnetic flux guiding (FG) device layers and steep side gap angles, which affect the controllability of main pole shape and write field uniformity.
Innovation Solution
The implementation of a PMR writer design with first and second FG devices in the write gap and side gaps, respectively, featuring a shallower side shield angle and a specific layer configuration (SP/NML1/FGL/NML2) to enhance magnetic flux guidance and uniformity, allowing for a more controllable main pole shape and improved write field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional steep side gap angles are used in PMR writers, then the structure is simpler, but the FG device layer uniformity deteriorates and main pole shape controllability is reduced
Solution Approach 1:
The patent changes the side gap angle parameter from conventional steep angles to shallower angles (specifically, the inner side of each side shield forms a shallower angle with the leading shield top surface). This parameter change enables more uniform FG device layers and better main pole shape controllability without fundamentally altering the device architecture.
2Manufacturing precision
If conventional FG device configurations are used, then the device structure is simpler, but the write field uniformity and main pole shape controllability deteriorate
Solution Approach 1:
The patent employs a composite multilayer structure for FG devices comprising spin polarization (SP) layer, first non-magnetic layer (NML1), flux guiding layer (FGL), and second non-magnetic layer (NML2). This composite structure enables precise control of magnetic flux and main pole shape while maintaining reproducible performance across devices.
3Manufacturing precision
If shallower side shield angles are implemented, then FG device layer uniformity is improved, but the manufacturing process becomes more complex
Solution Approach 1:
By optimizing the side gap angle parameter to a shallower configuration, the patent creates more favorable deposition geometry that enables uniform thin film formation. The shallower angle provides a more gradual surface for layer deposition, reducing the complexity of achieving uniform coverage compared to steep angles.
4Reliability
If the main pole shape is made more controllable, then write field uniformity is improved, but the device design complexity increases
Solution Approach 1:
The composite SP/NML1/FGL/NML2 layer structure provides independent control over different aspects of magnetic flux guidance. Each layer contributes specific functionality, enabling precise shaping of the main pole and uniform write field generation through the combined effect of multiple materials rather than a single complex geometry.
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 design achieves a more reproducible and uniform FG device performance, maintaining write field strength and gradient while ensuring tighter control over main pole parameters, thereby enhancing the reliability and efficiency of PMR writers.
Implementation Method 1
STO devices are based on a spin-torque-transfer effect that arises from the spin dependent electron transport properties of ferromagnetic (FM1)-spacer-ferromagnetic (FM2) multilayers. When spin polarized current from the FM1 layer passes through the spacer and FM2 layer in a current perpendicular-to-plane direction, the spin angular moment of electrons incident on the FM2 layer interacts with magnetic moments of the FM2 layer near the interface between the FM2 layer and the non-magnetic spacer. Through this interaction, the electrons transfer a portion of their angular momentum to the FM2 layer. As a result, spin-polarized current can switch (flip) the FM2 magnetization direction if the current density is sufficiently high.
Implementation Method 2
As a result, there is increased reluctance in the write gap so that more magnetic flux from the MP will be concentrated in a direction orthogonal to the ABS to assist writing.
Implementation Method 3
In a PMR writer, the main pole generates a large local magnetic field to change the magnetization direction of the medium in proximity to the writer.
Data Source
AI summary
A perpendicular magnetic recording writer has a main pole (MP) with a first flux guiding (FG) device in a write gap between the MP trailing side and a trailing shield, and a second FG device in the leading gap (LG) and each side gap (SG). The SG angle is reduced to 15° to 45° to enable conformal and more uniform FG device layers to be formed in the SG and LG. As a result, the MP shape and write field are more reproducible. To compensate for a thinner MP thickness at the air bearing surface that results from maintaining the track width at a shallower SG angle, an upper MP tip may be formed on the lower MP tip thereby generating a hexagonal shape for the combined MP tip. In this case, the second FG device conforms to the shape of the two upper MP tip sides and trailing side.