Heat-Assisted Magnetic Recording Medium Grain Isolation
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Solution Overview
Problem
The challenge is to reduce exchange coupling between magnetic grains and achieve a smaller magnetic cluster size to attain a surface recording density of 1 Tbit/inch² in heat-assisted magnetic recording media, while maintaining thermal stability, as conventional methods face limitations in miniaturizing magnetic grain size due to increased anisotropic magnetic field and grain size distribution.
Innovation Solution
A heat-assisted magnetic recording medium is developed with a substrate and underlayers, including an FePt or CoPt alloy magnetic layer with a granular structure, where the underlayers are composed of an amorphous alloy, a Cr alloy with added elements like Ti, Mo, W, V, Mn, or Ru, and a MgO underlayer, allowing for reduced grain size and improved magnetic isolation, and optionally a soft magnetic underlayer for enhanced write characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the magnetic grain size is reduced to increase surface recording density, then the recording capacity increases, but the thermal stability deteriorates
Solution Approach 1:
The patent changes the physical state of the magnetic layer by heating it to the Curie temperature or higher, temporarily altering its magnetic properties (coercive force) to enable writing, then allowing it to cool and regain high thermal stability for data retention
Solution Approach 2:
The patent utilizes the phase transition of the magnetic layer at the Curie temperature, where the material transitions from a magnetically stable state to a magnetically soft state, enabling recording operations at high density while maintaining thermal stability during data storage
2Reliability
If the crystal magnetic anisotropy constant Ku is increased to improve thermal stability, then the thermal stability improves, but the anisotropic magnetic field Hk increases making writing impossible
Solution Approach 1:
The patent dynamically changes the magnetic properties of the layer by controlling its temperature. At operating temperature, the layer exhibits high Ku for thermal stability; during writing, it is heated to temporarily reduce Hk below the recording head's capability, then cools to restore high Hk for data retention
Solution Approach 2:
The patent changes the temperature parameter of the magnetic layer to modulate its magnetic properties, using thermal energy to temporarily overcome the high anisotropic magnetic field barrier during writing operations while maintaining high Ku for thermal stability during data storage
3Reliability
If conventional recording methods are used with high Ku materials, then thermal stability is maintained, but the magnetic grain size cannot be reduced below 10 nm
Solution Approach 1:
The patent employs phase transition at the Curie temperature to temporarily reduce the magnetic hardness of high Ku materials, enabling the formation of smaller magnetic grains (6 nm or less) that would otherwise be impossible to write due to excessively high anisotropic magnetic fields
Solution Approach 2:
The patent changes the temperature parameter during the recording process to enable grain size reduction. By heating to Curie temperature or higher, the effective magnetic field barrier is reduced, allowing conventional recording heads to write to grains as small as 6 nm while the material's inherent high Ku ensures thermal stability when cooled
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
This approach effectively reduces exchange coupling and achieves a high surface recording density by forming small, uniformly sized magnetic crystal grains with reduced medium noise, enabling a magnetic storage device capable of 1 Tbit/inch² density.
Implementation Method 1
the magnetic layer is heated to the Curie temperature or higher so that the coercive force of the magnetic layer becomes equal to or lower than the recording magnetic field
Implementation Method 2
near-field light or the like is irradiated onto the medium, thereby causing localized heating of the medium surface
Data Source
AI summary
A heat-assisted magnetic recording medium that includes a substrate, underlayers formed on the substrate, and a magnetic layer which is formed on the underlayers and contains either an FePt alloy having an L10 structure or a CoPt alloy having an L10 structure as a main component, wherein the underlayers include a first underlayer formed from an amorphous alloy, a second underlayer formed from an alloy having a BCC structure containing Cr as a main component and also containing at least one element selected from among Ti, Mo, W, V, Mn and Ru, and a third underlayer formed from MgO. Also, a magnetic storage device that uses the heat-assisted magnetic recording medium.