High Resistivity Heat Sink Layer for HAMR Magnetic Stack
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Solution Overview
Problem
Magnetic storage drives face challenges in achieving higher areal storage density due to thermal stability limits of magnetic grains, where high magnetic anisotropy materials require energy assistance for data writing, and existing heat sink materials with low resistivity reduce coupling efficiency in heat-assisted magnetic recording (HAMR) systems.
Innovation Solution
A heat sink layer with high thermal conductivity (>1 W/mK) and electrical resistivity (>5×10−8 Ωm) is used in a magnetic stack, functioning as both a heat sink and a soft underlayer, made from materials like Al, Cu, or Si, to mitigate image charge effects and enhance coupling efficiency by reducing thermal spot size and maintaining data stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If materials with higher magnetic anisotropy energy are used to form magnetic grains, then thermal stability and data reliability are improved, but the difficulty of writing data increases and energy assistance is required
Solution Approach 1:
The patent applies preliminary heating to the magnetic recording layer before data writing. By pre-heating the medium to reduce magnetic anisotropy energy temporarily, the system enables easier data writing to high-anisotropy materials. The heating is performed in advance of the write operation, allowing the magnetic grains to become more receptive to the write field while maintaining thermal stability during data storage.
Solution Approach 2:
The system uses periodic heating cycles synchronized with the write operation. The magnetic recording layer is heated briefly during the write process and then allowed to cool. This periodic thermal assistance enables data writing to high-anisotropy materials without compromising long-term data reliability, as the material returns to its stable state after each write cycle.
2Temperature
If heat sink materials with low resistivity are used, then thermal conductivity is improved, but coupling efficiency in HAMR systems deteriorates
Solution Approach 1:
The patent changes the electrical resistivity parameter of the heat sink layer from low to high values. By selecting materials with high electrical resistivity (>5×10^-8 Ωm) but adequate thermal conductivity (>1 W/mK), the system reduces image charge effects and improves coupling efficiency in HAMR systems while maintaining the ability to sink heat from the magnetic recording layer.
Solution Approach 2:
The system employs composite material selection for the heat sink layer, choosing materials that combine high electrical resistivity with sufficient thermal conductivity. This composite property approach allows the heat sink to simultaneously improve coupling efficiency by reducing image charges and maintain thermal management functionality by conducting heat away from the recording layer.
3Area of moving object
If the thermal spot size is reduced to increase recording density, then areal storage density is improved, but heat removal from the magnetic recording layer becomes more difficult
Solution Approach 1:
The patent applies local quality enhancement by positioning a dedicated heat sink layer directly beneath the magnetic recording layer at the thermal spot location. This localized heat sinking structure ensures that even when the thermal spot size is reduced for high-density recording, heat is efficiently removed from the confined area where it is generated, preventing thermal accumulation that would compromise data stability.
Solution Approach 2:
The heat sink layer acts as an intermediary between the magnetic recording layer and the substrate. It mediates heat transfer by providing a thermal conduction pathway that efficiently removes heat from the small thermal spot area. This intermediary structure enables the system to maintain small thermal spots for high recording density while ensuring adequate heat removal through the heat sink's high thermal conductivity.
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 solution effectively increases coupling efficiency and data stability by rapidly removing heat from the magnetic recording layer, allowing for smaller thermal spots and improved recording density while maintaining data reliability.
Implementation Method 1
the heat sink layer is configured to function as a heat sink... rapidly removing heat from the magnetic recording layer
Implementation Method 2
a near field transducer (NFT) positioned proximate the write pole that radiates energy
Data Source
AI summary
A layer configured for use in a magnetic stack has electrical resistivity greater than about 5×10−8 Ωm and thermal conductivity greater than about 1 W/mK. In some arrangements, the magnetic stack includes a substrate with the layer disposed over the substrate, a magnetic recording layer disposed over the layer, and a thermal resist layer disposed between the layer and the magnetic recording layer. In some arrangements, the layer is configured to function as a heat sink and a soft under layer. A system that incorporates the layer can include a magnetic write pole, a near field transducer (NFT) positioned proximate the write pole that radiates energy.