HAMR Multilayer Underlayer for Laser Power Reduction
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Solution Overview
Problem
In heat-assisted magnetic recording (HAMR) media, optimizing the thermal conductivity of the underlayer to achieve a high thermal gradient while minimizing laser power is challenging, as high thermal conductivity can lead to rapid heat distribution and low thermal conductivity can cause lateral heat spreading, potentially overwriting adjacent data tracks.
Innovation Solution
A multilayered underlayer comprising a thermal barrier layer of MgO and TiO, with a seed layer containing MgO and nitrogen, is introduced between the heat-sink layer and the recording layer, providing higher thermal resistivity and reducing laser power requirements while maintaining a high thermal gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer MgO thermal barrier/seed layer is used, then the structure is simple and easy to manufacture, but the thermal conductivity is either too high (requiring more laser power) or too low (causing lateral heat spreading)
Solution Approach 1:
The single-layer MgO underlayer is segmented into multiple layers with different compositions and functions: a MgO-TiO thermal barrier layer (higher thermal resistivity) and a MgO-N seed layer (lower thermal resistivity). This segmentation allows independent optimization of thermal management and magnetic seed functions, achieving high thermal gradient while maintaining structural complexity at a manageable level.
Solution Approach 2:
The underlayer uses composite material structures: MgO-TiO for enhanced thermal barrier properties and MgO-N for improved magnetic seeding. These composite layers provide tailored thermal and magnetic properties that cannot be achieved with pure MgO, reducing laser power requirements while preventing lateral heat spread.
2Speed
If high thermal conductivity material is used in the underlayer, then heat is distributed rapidly (reducing thermal gradient), but laser power requirements increase
Solution Approach 1:
Different regions of the underlayer have different thermal conductivities tailored to local requirements: the MgO-TiO thermal barrier layer has higher thermal resistivity to maintain high thermal gradient and reduce laser power, while the MgO-N seed layer has lower thermal resistivity to provide adequate thermal coupling. This local quality differentiation resolves the contradiction between heat distribution speed and laser power consumption.
3Use of energy by moving object
If low thermal conductivity material is used in the underlayer, then laser power is reduced, but heat spreads laterally causing overwriting of adjacent data tracks
Solution Approach 1:
The underlayer is segmented into vertical layers with distinct thermal properties: the MgO-TiO thermal barrier layer provides high thermal resistivity to reduce lateral heat spread, while the MgO-N seed layer provides controlled thermal coupling. This vertical segmentation prevents lateral heat diffusion that would occur with a uniform low-conductivity layer, while still reducing overall laser power requirements compared to high-conductivity materials.
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 multilayered underlayer achieves reduced laser power usage while maintaining high thermal gradient and signal quality, improving signal-to-noise ratio, transition jitter, and corrosion resistance compared to conventional single-layer configurations.
Implementation Method 1
The underlayer is typically a single layer or multilayer of a material that is a good thermal conductor, like Cu, Au, Ag, Cr, Mo or W or other suitable metals or metal alloys. However, even with the use of a heat-sink, it is difficult to minimize laser power while still providing a high thermal gradient to the recording layer.
Implementation Method 2
If the thermal conductivity of the MgO thermal barrier/seed layer is too high the heat from the NFT will be distributed too rapidly, which will require more laser power to heat the FePt material.
Implementation Method 3
The most common type of proposed HAMR disk drive uses a laser source and an optical waveguide with a near-field transducer (NFT). In some proposed HAMR systems, the magnetic recording material is heated to near or above its Curie temperature.
Implementation Method 4
The FePt alloy requires deposition at high temperature or subsequent high-temperature annealing to achieve the desired chemical ordering to the L10 phase.
Data Source
AI summary
A heat-assisted magnetic recording (HAMR) medium has a multilayered underlayer between the heat-sink layer and the recording layer. One embodiment of the underlayer is a multilayer of a thermal barrier layer consisting essentially of MgO and TiO, and a seed layer containing MgO and nitrogen (N) directly on the thermal barrier layer, with the recording layer on and in contact with the seed layer. The interface between the thermal barrier layer and the seed layer contains Ti and N, some of which may be present as TiN to act as a diffusion barrier to prevent diffusion of the Ti into the recording layer. The Ti-containing thermal barrier layer has a higher thermal resistivity than the conventional MgO thermal barrier/seed layer and thus allows for reduced laser power to the recording layer while still achieving a high thermal gradient at the recording layer.