MgXO Insulating Layer for TAR Disk Heat Control
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Solution Overview
Problem
In thermally-assisted recording (TAR) disk drives, there is a challenge in optimizing the thermal conductivity of the insulating layer beneath the FePt recording layer to prevent excessive heat distribution and lateral heat spreading, which can lead to data overwriting in adjacent tracks.
Innovation Solution
A solid substitution crystalline alloy MgXO is used as the insulating layer, where X is nickel (Ni) or cobalt (Co), with a composition of (Mg(100-y)Xy)O, having a lower thermal conductivity than traditional MgO, allowing for controlled heat distribution and matching the crystalline lattice of MgO for proper growth of the FePt layer, optionally combined with a pure MgO layer to optimize thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the thermal conductivity of the MgO insulating layer is increased, then heat is distributed more rapidly reducing laser power requirements, but heat spreads laterally through the recording layer causing data overwriting in adjacent tracks
Solution Approach 1:
The patent changes the thermal conductivity parameter of the insulating layer by substituting MgO with MgXO alloy, where X is a metal element with lower thermal conductivity than MgO. This parameter change allows the layer to retain sufficient heat for writing while reducing lateral heat spread to adjacent tracks.
Solution Approach 2:
The patent creates a composite insulating layer using MgXO alloy combining MgO with metal elements (Ni, Co, Cu, Zn, Mn, or Al) in specific proportions. This composite structure achieves optimal thermal conductivity by leveraging the properties of both MgO and the added metal elements.
2Reliability
If the thermal conductivity of the insulating layer is decreased to prevent lateral heat spreading, then data integrity is maintained, but more laser power is required to heat the FePt material
Solution Approach 1:
The patent optimizes the thermal conductivity parameter within a specific range (0.5-2.0 W/m·K) by controlling the composition and thickness of the MgXO layer. This parameter optimization ensures the layer is insulating enough to prevent lateral heat spread but conductive enough to allow efficient heat transfer from the laser to the FePt recording layer.
Solution Approach 2:
The patent creates local quality differences in the insulating layer by using different MgXO compositions or thicknesses in different regions or layers. The first MgXO layer has different properties than the second MgXO layer, allowing optimization of heat confinement in one region while maintaining heat transfer efficiency in another.
3Reliability
If a thicker MgO layer is used to reduce thermal conductivity and prevent lateral heat spreading, then data integrity is maintained, but the structural integrity and growth of the FePt layer may be compromised
Solution Approach 1:
The patent uses MgXO composite materials that maintain crystalline structure compatibility with FePt while providing reduced thermal conductivity. The metal elements (Ni, Co, Cu, Zn, Mn, or Al) are selected and proportioned to ensure lattice matching and proper epitaxial growth of the FePt recording layer.
Solution Approach 2:
The patent segments the insulating layer into multiple MgXO layers with different compositions or thicknesses. The first MgXO layer (in contact with FePt) is optimized for crystalline growth support, while the second MgXO layer is optimized for heat confinement, achieving both manufacturing precision and data integrity.
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 solution allows for reduced laser power requirements and minimizes lateral heat spreading, maintaining data integrity by achieving the right balance in thermal conductivity, thus optimizing heat control to the recording layer.
Implementation Method 1
If the thermal conductivity of the MgO insulating layer is too high the heat from the NFT will be distributed too rapidly... If the thermal conductivity of the MgO insulating layer is too low the heat from the NFT will be confined to the recording layer and will spread laterally through the recording layer
Implementation Method 2
The magnetic recording material is heated to near or above its Curie temperature
Implementation Method 3
the magnetic recording material is heated to near or above its Curie temperature. The recorded data is then read back at ambient temperature by a conventional magnetoresistive read head
Data Source
AI summary
A thermally-assisted recording (TAR) disk has an improved insulating layer beneath the chemically-ordered FePt (or CoPt) alloy recording layer. The insulating layer is a solid substitution crystalline alloy MgXO, where the element X is selected from nickel (Ni) and cobalt (Co). The composition of the MgXO crystalline solid substitutional alloy is of the form (Mg(100-y)Xy)O where y is between 10 and 90, and more preferably between 20 and 80. An optional layer of crystalline “pure” MgO may be located between the MgXO layer and the FePt recording layer and in contact with the recording layer, or between an underlayer and the MgXO layer.