Iridium Underlayer for HAMR Media Thermal Stability
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Solution Overview
Problem
Conventional perpendicular magnetic recording (PMR) media face limitations in areal density due to superparamagnetic limits and thermal stability issues, which are addressed by using heat-assisted magnetic recording (HAMR) media with higher magnetocrystalline anisotropy materials like L10 FePt alloys, but these require a write assist mechanism and have wider magnetic write widths, limiting further density increases.
Innovation Solution
The use of an Iridium-based underlayer in HAMR media structures, which acts as an orientation control layer and diffusion barrier, allowing for higher deposition rates and better control over morphology and structure, replacing conventional Magnesium Oxide (MgO) underlayers to enhance thermal stability and writability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If HAMR media with higher magnetocrystalline anisotropy materials (e.g., L10 FePt) is used to increase areal density, then thermal stability is improved, but the magnetic write width increases, limiting further density increases
Solution Approach 1:
The patent applies local quality by introducing an Iridium-based underlayer with specific magnetic properties (high magnetocrystalline anisotropy) that is localized at the interface with the magnetic recording layer. This underlayer has different magnetic characteristics from conventional underlayers, creating a localized region that enhances thermal stability and controls magnetic flux distribution, thereby reducing the overall magnetic write width while maintaining thermal stability.
2Ease of manufacture
If conventional MgO underlayer is used in HAMR media, then manufacturing process is simple, but deposition rate is low and control over morphology is limited
Solution Approach 1:
The patent applies parameter changes by transitioning from MgO underlayer to Iridium-based underlayer, which fundamentally changes the material parameters (composition, crystal structure, magnetic properties). This material substitution enables higher deposition rates and better control over layer morphology while maintaining ease of manufacture through standard deposition processes, thus resolving the contradiction between manufacturing simplicity and productivity.
3Area of stationary object
If higher magnetocrystalline anisotropy materials are used to achieve smaller grain sizes, then areal density is improved, but writability becomes more difficult
Solution Approach 1:
The Iridium-based underlayer acts as an intermediary between the substrate and the magnetic recording layer. It provides a controlled interface that facilitates heat transfer during writing while maintaining magnetic flux confinement. This intermediary layer enables smaller grain sizes (improving areal density) while maintaining writability by mediating the interaction between the write head and the high-anisotropy magnetic layer.
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 Iridium-based underlayer improves production yields, maintains high thermal stability, and allows for smaller grain sizes while maintaining high magnetic anisotropy, enabling higher areal densities in HAMR media without degrading magnetic properties, thus overcoming the constraints of conventional PMR media.
Implementation Method 1
acts as an orientation control layer and diffusion barrier, allowing for higher deposition rates and better control over morphology and structure
Implementation Method 2
acts as an orientation control layer and diffusion barrier
Implementation Method 3
HAMR media is temporarily heated to reduce its coercivity below that of an applied magnetic write field from a recording head, i.e., the temperature of the recording location on the HAMR media is increased in order to sufficiently lower the location's Ku to allow a change to its magnetic orientation
Implementation Method 4
HAMR media is made of magnetic materials or compounds with substantially higher magnetocrystalline anisotropy (indicated by the magnetic anisotropy constant, Ku) than that of non-HAMR media
Data Source
AI summary
A heat-assisted magnetic recording (HAMR) media stack is provided in which Iridium (Ir)-based materials may be utilized as a secondary underlayer instead of a Magnesium Oxide (MgO) underlayer utilized in conventional media stacks. Such Ir-based materials may include, e.g., pure Ir, Ir-based alloys, Ir-based compounds, as well as a granular Ir layer with segregants. The use of Ir or Ir-based materials as an underlayer provide advantages over the use of MgO as an underlayer. For example, DC sputtering can be utilized to deposit the layers of the media stack, where the deposition rate of Ir is considerably higher than that of MgO resulting in higher manufacturing production yields. Further still, less particles are generated during Ir-based layer deposition processes, and Ir-based underlayer can act as a better heat sink. Further still, the morphology and structure of a recording layer deposited on an Ir-based layer can be better controlled.