Magnetic Recording Medium Underlayer Design for Heat-Assisted Magnetic Recording
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Solution Overview
Problem
Conventional heat-assisted magnetic recording methods face challenges in achieving sufficient (001) orientation of the magnetic layer, leading to inadequate signal-to-noise ratio (SNR) due to insufficient underlayer performance, which also fails to effectively control heat spot expansion and reduce noise.
Innovation Solution
A magnetic recording medium is designed with a stacked configuration including a substrate, a first underlayer with Mo as the main component, a second underlayer containing Mo and an oxide, and a magnetic layer with an L10 type crystal structure. The second underlayer has a non-granular structure and includes oxides of Cr, Mo, Nb, Ta, V, or W, while a barrier layer and orientation control layer enhance the (001) orientation and crystallinity, suppressing heat spot expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional underlayer materials (MgO, CrN, TiN) are used, then the magnetic layer can be formed, but the (001) orientation is insufficient leading to low signal-to-noise ratio
Solution Approach 1:
The patent employs a composite underlayer structure consisting of multiple layers with different materials and functions. The first underlayer uses MgO as the base material, while the second underlayer introduces a compound layer containing transition metal elements (Mn, Fe, Co, Ni, Cu, Zn, or Al) to enhance the (001) orientation of the magnetic layer. This composite structure combines the advantages of both materials to achieve both adequate formation and high orientation of the magnetic layer, thereby improving the signal-to-noise ratio.
2Ease of manufacture
If the underlayer structure is simplified, then the manufacturing process is easier, but the heat spot expansion cannot be effectively controlled
Solution Approach 1:
The patent divides the underlayer into two distinct segments: a first underlayer and a second underlayer. The first underlayer (MgO-based) provides a stable foundation and facilitates magnetic layer formation, while the second underlayer (compound layer with transition metal elements) specifically controls heat spot expansion during heat-assisted magnetic recording. This segmentation allows each layer to perform its specific function optimally, effectively controlling heat spot expansion while maintaining manufacturing feasibility through a clear two-layer structure.
3Reliability
If high Ku material is used in magnetic layer, then thermal fluctuation is reduced, but the volume of magnetic particles must be minimized which narrows transition width
Solution Approach 1:
The patent utilizes parameter changes in the underlayer structure to enable the use of high Ku materials in the magnetic layer. By introducing the compound layer with transition metal elements in the second underlayer, the (001) orientation is enhanced, which allows high Ku materials to be used effectively. This parameter change in the underlayer composition and structure enables the magnetic layer to achieve both high thermal fluctuation resistance and appropriately sized magnetic particles for reliable recording.
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 configuration significantly improves the signal-to-noise ratio (SNR) by enhancing the (001) orientation of the magnetic layer and effectively controlling heat distribution, resulting in reduced noise and increased recording density.
Implementation Method 1
a first underlayer; a second underlayer... The first underlayer is a crystalline layer that includes Mo as a main component. The second underlayer is a crystalline layer that includes a material containing Mo as a main component and that includes an oxide
Implementation Method 2
the underlayer of the heat-assisted magnetic recording medium is needed to have a function as a temperature control layer. That is, when a heat-assisted magnetic recording medium is irradiated with near-filed light to locally heat the surface of the heat-assisted magnetic recording medium, the expansion of the heat spot needs to be suppressed
Implementation Method 3
as a material that constitutes a magnetic layer, a material having a high Ku is used, such as FePt having an L10 type crystal structure (Ku 7×107 erg/cm3), or CoPt having an L10 type crystal structure (Ku 5×107 erg/cm3)
Data Source
AI summary
A magnetic recording medium includes: a substrate; a first underlayer; a second underlayer; and a magnetic layer including an alloy having a L10 type crystal structure with a (001) orientation. The substrate, the first underlayer, the second underlayer, and the magnetic layer are stacked in this order. The first underlayer is a crystalline layer that includes Mo as a main component. The second underlayer is a crystalline layer that includes a material containing Mo as a main component and that includes an oxide. The content of the oxide in the second underlayer is in a range of from 2 mol % to 30 mol %. The oxide is an oxide of one or more kinds of elements selected from a group consisting of Cr, Mo, Nb, Ta, V, and W.