Laminated PMR Write Pole Reducing Remanence
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Solution Overview
Problem
Perpendicular magnetic recording (PMR) technologies face challenges with head-induced data erasure due to remanent magnetization and sharp pointed geometry of the write pole, which affects overwrite performance and signal to noise ratio.
Innovation Solution
A laminated main pole layer is designed with a magnetic layer such as FeCo or FeCoNi and a non-magnetic spacer like Ru or Al2O3, where the trailing magnetic layer is thicker than the other magnetic layers, and the magnetic layers are exchange decoupled or anti-ferromagnetically coupled through the non-magnetic spacer, to minimize remanence and improve magnetic moment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional single-layer main pole layer with sharp pointed geometry is used, then high magnetic moment and write field are achieved, but remanent magnetization causes head-induced data erasure and poor overwrite performance
Solution Approach 1:
The main pole layer is divided into multiple magnetic layers separated by non-magnetic spacer layers. This segmentation creates exchange decoupling or anti-ferromagnetic coupling between layers, reducing remanent magnetization while maintaining write field strength, thereby preventing head-induced data erasure and improving overwrite performance
Solution Approach 2:
The patent uses composite laminated structures combining magnetic layers (e.g., CoFeB, CoFe) with non-magnetic spacer layers (e.g., Ru, Rh, Ir). This composite approach enables control of magnetic properties through interlayer coupling, reducing remanence while preserving high moment characteristics for effective writing
2Loss of energy
If magnetic layers are made thinner to reduce remanence, then data erasure is minimized, but magnetic moment and write field intensity decrease
Solution Approach 1:
Instead of using a single thin layer, the patent segments the magnetic material into multiple thin layers separated by non-magnetic spacers. The total magnetic moment is distributed across layers, with the non-magnetic spacers providing exchange decoupling that reduces remanence while the cumulative effect of multiple layers maintains sufficient write field strength
Solution Approach 2:
Non-magnetic spacer layers (Ru, Rh, Ir) act as intermediaries between magnetic layers. These spacers control the coupling strength between adjacent magnetic layers, enabling exchange decoupling or anti-ferromagnetic coupling that reduces remanence while allowing the stacked magnetic layers to collectively provide the necessary magnetic moment
3Reliability
If a thicker trailing magnetic layer is added to improve overwrite performance, then write field gradient is enhanced, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent applies local quality by making the trailing magnetic layer thicker than other magnetic layers in the laminate. This local variation in thickness concentrates magnetic flux at the trailing edge, enhancing the write field gradient and overwrite performance in the critical region where it is most needed, while keeping other regions simpler
Solution Approach 2:
The differentiated thickness of the trailing magnetic layer is achieved through segmented fabrication approaches, where the trailing layer is deposited or patterned separately with different parameters than other layers, allowing optimization of local magnetic properties without redesigning the entire structure
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 reduces remanence, enhances overwrite performance, and improves signal to noise ratio by maintaining high magnetic moment while minimizing data erasure and increasing write field intensity at the trailing edge.
Implementation Method 1
the magnetic layers are exchange decoupled or anti-ferromagnetically coupled through the non-magnetic spacer
Implementation Method 2
the magnetic layers are exchange decoupled or anti-ferromagnetically coupled through the non-magnetic spacer
Implementation Method 3
Magnetic flux in the write pole layer 10 is generated by coils 6 and passes through the pole tip into a magnetic recording media 4
Data Source
AI summary
A laminated write pole layer for a PMR write head is disclosed in which a plurality of “n” magnetic layers and “n−1” non-magnetic spacers are formed in an alternating fashion on a substrate. The non-magnetic spacers promote exchange decoupling or antiferromagnetic coupling between adjacent magnetic layers. Writability is improved when the trailing magnetic layer has a thickness greater than the thickness of other magnetic layers and preferably >25% of the total thickness of the magnetic layers. The thicknesses of the other magnetic layers may be equal or may become progressively smaller with increasing distance from the trailing magnetic layer. In another embodiment, the non-magnetic spacer between the trailing magnetic layer and the nearest magnetic layer is replaced by a magnetic spacer made of a soft magnetic material to promote magnetic coupling and effectively increase the thickness of the trailing magnetic layer.