Laminated Main Pole Layer for Perpendicular Magnetic Recording Heads
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Solution Overview
Problem
Perpendicular magnetic recording (PMR) technologies face challenges with head-induced data erasure due to remanent magnetization in the main pole layer, requiring a solution that balances high magnetic moment, low coercivity, and reduced remanence while being compatible with current manufacturing processes.
Innovation Solution
A laminated main pole layer structure is developed, comprising a thin amorphous material layer and a high moment material like FeCo, with an alignment layer to control grain structure and reduce remanence, using a configuration such as [(B/M)/A]n/(B/M)/cap or [(B/M/B/M)/A]n/(B/M/B/M)/cap, where the amorphous layer breaks exchange coupling and the cap layer serves as a CMP stop, implemented through sputter deposition and annealing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high moment FeCo material is used in the main pole layer, then the saturation magnetic flux density (Bs) is improved to above 22 kG, but the remanent magnetization increases causing head-induced data erasure
Solution Approach 1:
The main pole layer is divided into multiple thin FeCo sub-layers separated by Ru coupling layers. This segmentation allows the total saturation magnetic flux density to be maintained while reducing remanent magnetization through anti-parallel magnetic coupling between adjacent FeCo layers, where the remanent moments of individual layers cancel each other out
Solution Approach 2:
A composite laminated structure is created combining FeCo high moment material with Ru non-magnetic coupling layers. This composite material system achieves both high saturation magnetic flux density from the FeCo layers and reduced remanent magnetization through the anti-ferromagnetic coupling effect at the Ru interfaces
2Power
If the pole neck height is reduced to increase write field magnitude, then the field gradient is improved, but manufacturing process tolerance becomes difficult to meet
Solution Approach 1:
The pole neck height is optimized to a specific range (0.05-0.15 microns) to achieve the optimal balance between write field magnitude and manufacturing tolerance. The flare angle is also adjusted within specific ranges (30-60 degrees) to enhance field gradient while maintaining manufacturability, representing precise parameter optimization
3Power
If the flare angle is increased to enhance field gradient, then the write field distribution is improved, but adjacent track erasure increases due to large fringe field
Solution Approach 1:
The flare angle is optimized within a specific range (30-60 degrees) to achieve optimal field gradient while controlling fringe field effects. This parameter optimization balances the beneficial field distribution with the harmful adjacent track erasure, representing a compromise solution through precise parameter control
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
The laminated structure effectively minimizes pole erasure, maintains high magnetic moment for high areal density recording, and reduces anisotropy field and coercivity, ensuring compatibility with existing manufacturing flows.
Implementation Method 1
the amorphous layer breaks exchange coupling and the cap layer serves as a CMP stop
Implementation Method 2
implemented through sputter deposition and annealing processes
Implementation Method 3
implemented through sputter deposition and annealing processes
Data Source
AI summary
A laminated main pole layer is disclosed in which a non-AFC scheme is used to break the magnetic coupling between adjacent high moment layers and reduce remanence in a hard axis direction while maintaining a high magnetic moment and achieving low values for Hch, Hce, and Hk. An amorphous material layer with a thickness of 3 to 20 Angstroms and made of an oxide, nitride, or oxynitride of one or more of Hf, Zr, Ta, Al, Mg, Zn, or Si is inserted between adjacent high moment stacks. The laminated structure also includes an alignment layer below each high moment layer within each stack. In one embodiment, a Ru coupling layer is inserted between two high moment layers in each stack to introduce an AFC scheme. An uppermost Ru layer is used as a CMP stop layer. A post annealing process may be employed to further reduce the anisotropy field (Hk).