Granular Magnetic Recording Medium for Heat-Assisted High Density
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Solution Overview
Problem
Magnetic recording media for heat-assisted recording devices face challenges in achieving high density and enhanced signal-to-noise ratio (SNR) due to the thermal stability issues with decreasing magnetic crystal grain sizes and the obstacles posed by thick heat dissipation layers, which lead to surface irregularities and unstable head flying.
Innovation Solution
A magnetic recording medium with a granular structure comprising a magnetic portion and a non-magnetic portion, where the non-magnetic portion includes a carbon-based material, such as C or B4C, and is recessed with respect to the magnetic portion, forming moderate surface irregularities that enhance heat dissipation and SNR, while maintaining high recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the size of magnetic crystal grains is reduced to increase recording density, then recording density is improved, but thermal stability of recording magnetization drops
Solution Approach 1:
The magnetic recording layer uses a composite granular structure combining L10 ordered alloy (high magnetocrystalline anisotropy) with non-magnetic material (SiO2 or TiO2). This composite structure enables small magnetic crystal grains (for high density) while maintaining thermal stability through the high anisotropy of the L10 ordered alloy phase.
Solution Approach 2:
The invention changes the magnetocrystalline anisotropy parameter by using L10 ordered alloys with high Ku values. This parameter change allows the magnetic crystal grains to maintain stable magnetization even at reduced sizes, resolving the contradiction between density and thermal stability.
2Temperature
If a thick heat dissipation layer is added to improve heat dissipation, then heat dissipation is improved, but surface irregularities increase causing unstable head flying
Solution Approach 1:
Instead of adding a thick heat dissipation layer that affects the entire surface, the invention creates localized heat dissipation pathways through the granular structure itself. The non-magnetic portions between magnetic crystal grains provide localized thermal management without creating widespread surface irregularities.
Solution Approach 2:
The invention extracts the heat dissipation function from a separate thick layer and integrates it into the granular magnetic recording layer structure itself, eliminating the need for additional heat dissipation layers that would cause surface irregularities.
3Reliability
If L10 ordered alloy is used to achieve high magnetocrystalline anisotropy, then thermal stability is improved, but manufacturing complexity increases due to specific underlayer requirements
Solution Approach 1:
The invention changes the lattice structure parameter of the underlayer from conventional cubic structures to tetragonal MgO or SrTiO3. This parameter change provides appropriate lattice matching for L10 ordered alloys, enabling high magnetocrystalline anisotropy while managing manufacturing complexity through standardized deposition processes.
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 proposed solution results in a magnetic recording medium with improved heat dissipation characteristics and enhanced SNR, allowing for high-density recording and stable read-write performance by optimizing the surface roughness and heat dissipation.
Implementation Method 1
a SiO2 non-magnetic material segregates so as to surround the periphery of CoCrPt magnetic crystal grains, so that the individual magnetic crystal grains of CoCrPt are magnetically isolated by the SiO2 non-magnetic material
Implementation Method 2
Heat-assisted recording exploits the temperature dependence of the magnetic anisotropy constant Ku of magnetic materials, i.e., the characteristic whereby Ku becomes smaller at higher temperatures
Implementation Method 3
the thermal stability of recording magnetization drops as the size of the magnetic crystal grains decreases
Data Source
AI summary
Disclosed are a magnetic recording medium for a heat-assisted recording device, which has a high SNR at high density, and a manufacturing method thereof. The magnetic recording medium includes a non-magnetic substrate; a magnetic recording layer; a protective layer; and a liquid lubricating layer. The magnetic recording layer has a granular structure formed by magnetic portions and non-magnetic portions that surround the magnetic portions in which the non-magnetic portions between adjacent magnetic portions are recessed with respect to the magnetic portions. The non-magnetic portions have a volume percentage based on total volume of the granular structure ranging from 15 vol % to 30 vol % and include a carbon-based material. The magnetic recording medium has a surface having an arithmetic mean roughness Ra and an average length of roughness curve elements RSm such that Ra/RSm ranges from 0.05 to 0.15.