Antiferromagnetic Coupled Return Pole for Magnetic Head Stability
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Solution Overview
Problem
Conventional magnetic recording heads face instability issues due to magnetically dynamic first poles and magnetic coupling with shields, leading to reader instability and performance drawbacks.
Innovation Solution
Incorporating an antiparallel coupled (AC) structure in the return pole of the magnetic recording head, which reduces magnetic activity and domain formation, and uses antiferromagnetically coupled ferromagnetic layers with nonmagnetic spacer layers to enhance stability and reduce magnetostatic coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional return pole is used in the magnetic recording head, then the device is simpler in structure, but the return pole becomes magnetically dynamic and unstable, causing reader instability
Solution Approach 1:
The return pole is constructed using composite magnetic layers including ferromagnetic layers and nonmagnetic spacer layers arranged in a multilayer structure. This composite construction allows the return pole to achieve magnetic stability through antiferromagnetic coupling between layers, resolving the instability issue while maintaining structural integrity
Solution Approach 2:
The return pole is divided into multiple discrete layers (ferromagnetic layers separated by nonmagnetic spacer layers) rather than being a single homogeneous structure. This segmentation enables independent control of magnetic properties in each layer, allowing the system to achieve stability through the collective behavior of coupled layers
2Power
If the return pole is made magnetically active to improve writer performance, then writing capability is enhanced, but magnetic coupling with the shield increases causing reader instability
Solution Approach 1:
Nonmagnetic spacer layers are introduced as intermediary elements between ferromagnetic layers in the return pole structure. These spacer layers mediate the magnetic interaction, enabling controlled antiferromagnetic coupling that reduces unwanted magnetic coupling with the shield while preserving writing capability
Solution Approach 2:
The magnetic properties of the return pole are modified by changing the composition and thickness parameters of the layered structure. By adjusting the thickness of nonmagnetic spacer layers and the magnetic moments of ferromagnetic layers, the system achieves optimal balance between writing power and magnetic coupling reduction
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 AC structure improves the stability of the return pole, allowing it to reach a single domain state, reducing domain wall formation and remanent dynamics, thereby enhancing the performance of both the writer and reader transducers.
Implementation Method 1
an antiferromagnetic (AFM) layer may also be provided in the shield 18
Implementation Method 2
magnetic coupling between the first pole 22 and the shield 18 may be a source of reader instability
Data Source
AI summary
A method and system provide a magnetic head having an air-bearing surface (ABS). The magnetic head includes a read transducer and a write transducer. The read transducer includes a first shield and a read sensor. The write transducer includes a main pole, at least one coil for energizing the main pole and a return pole between the read sensor and the main pole. The return pole includes an antiparallel coupling (AC) pole structure. The AC pole structure includes a plurality of ferromagnetic layers interleaved with at least one nonmagnetic layer. The ferromagnetic layers and the nonmagnetic spacer layer(s) are substantially parallel. The ferromagnetic layers and the nonmagnetic spacer layer(s) are substantially perpendicular to the ABS. The magnetic moment of each of the ferromagnetic layers is aligned antiparallel with the magnetic moment of a nearest neighbor of the ferromagnetic layers.