Composite Magnetic Recording Layer for High Areal Density
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Solution Overview
Problem
Conventional perpendicular magnetic recording media face challenges in achieving high areal density and coercivity reduction, limiting the thickness and performance of magnetic recording layers.
Innovation Solution
A composite hard magnetic recording layer is introduced, comprising a hard magnetic layer and a capping magnetic layer with lower coercivity, which includes a granular structure of columnar grains extending between the two layers, allowing for a thicker recording layer and reduced coercivity, and can be formed using sputtering epitaxial growth processes with specific alloy compositions like FePt—C and CoPt—TiO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional single-layer magnetic recording layer is used, then the structure is simple and easy to manufacture, but the coercivity is high and the areal density is limited
Solution Approach 1:
The magnetic recording layer is segmented into multiple sub-layers with different magnetic properties. The first sub-layer has higher coercivity and the second sub-layer has lower coercivity, allowing the composite structure to achieve reduced overall coercivity while maintaining thermal stability, resolving the contradiction between simple structure and coercivity control.
Solution Approach 2:
The patent uses composite magnetic materials by combining two different magnetic sub-layers with distinct coercivity characteristics. This composite structure enables the recording layer to exhibit reduced effective coercivity while maintaining structural integrity and manufacturability, addressing both the simplicity and performance requirements.
2Reliability
If the magnetic recording layer is made thinner to reduce coercivity, then the coercivity decreases, but the signal-to-noise ratio deteriorates
Solution Approach 1:
By segmenting the recording layer into two sub-layers, the patent achieves coercivity reduction through the softer second sub-layer while the first sub-layer maintains sufficient thickness to preserve signal strength. This segmentation allows independent optimization of each sub-layer thickness to balance coercivity and signal-to-noise ratio.
Solution Approach 2:
Different regions of the recording layer are assigned different magnetic qualities - the first sub-layer provides high coercivity for thermal stability while the second sub-layer provides low coercivity for ease of writing. This local differentiation allows the overall layer to maintain adequate thickness for signal strength while achieving reduced effective coercivity.
3Measurement precision
If the magnetic recording layer is made thicker to improve signal-to-noise ratio, then the signal strength increases, but the coercivity increases and areal density is limited
Solution Approach 1:
The segmented structure allows the recording layer to be thicker overall while maintaining low effective coercivity. The first sub-layer can be thicker to provide signal strength, while the second sub-layer compensates by providing low coercivity, enabling thick layers without the coercivity penalty of conventional single-layer structures.
Solution Approach 2:
The composite magnetic layer combines materials with different coercivity characteristics, enabling the overall layer to be thicker for improved signal-to-noise ratio while the softer magnetic component keeps the effective coercivity low, thus allowing higher areal density without sacrificing signal quality.
4Quantity of substance
If conventional magnetic recording media is used, then the areal density is limited to below 800 Gbits/in2, but the structure and materials are simpler
Solution Approach 1:
The segmented recording layer structure enables higher areal density by allowing optimized thickness and composition for each sub-layer, facilitating better magnetic property control at higher densities. The first sub-layer optimizes for thermal stability while the second optimizes for writeability, enabling densities above 800 Gbits/in2.
Solution Approach 2:
The use of composite magnetic materials in the recording layer enables higher areal density through improved magnetic property control. The combination of different magnetic materials allows optimization of both thermal stability and writeability, key requirements for high-density storage, while maintaining a relatively straightforward two-layer 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 composite recording layer achieves increased signal-to-noise ratio, allows for thicker recording layers, and reduces coercivity, enabling higher areal density and improved performance in disk drives, including the use of FePt in unassisted PMR and lower temperatures in HAMR devices.
Implementation Method 1
can be formed using sputtering epitaxial growth processes
Implementation Method 2
can be formed using sputtering epitaxial growth processes
Implementation Method 3
current is passed through the coil 104 to create magnetic flux within the write pole 102. The magnetic flux passes from the write pole 102, through the disk 105, and across to the opposing pole 103 to record in the PMR layer 150
Data Source
AI summary
A composite hard magnetic recording layer for a magnetic storage comprises a hard magnetic layer and a capping layer. The composite recording layer has a crystal structure where crystal grains include a portion within the magnetic layer and a portion within the capping layer.