Magnetic Recording Medium Underlayer Design for High SNR
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Solution Overview
Problem
Existing magnetic recording technologies face challenges in reducing magnetic crystal grain size and exchange coupling between grains while maintaining high signal-to-noise ratio (SNR) without deteriorating the ordering of crystal grains in L10 type alloys, which affects the crystal magnetic anisotropy and recording density.
Innovation Solution
A magnetic recording medium with a substrate, a magnetic layer having an L10 type crystal structure, and multiple underlayers, including at least one crystalline underlayer with a (100) orientation composed primarily of W and additional elements like Fe, Ni, Co, Hf, Zr, Y, Be, Ce, or Sc, which promotes uniform crystal grain growth and reduces exchange coupling, thereby enhancing SNR without compromising grain ordering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If grain boundary material is added to reduce magnetic grain size and exchange coupling, then medium SNR is improved, but ordering of L10 type alloy crystal grains deteriorates
Solution Approach 1:
The patent divides the underlayer into multiple distinct layers (first underlayer, second underlayer, third underlayer) with different compositions and functions. The first underlayer promotes L10 ordering, the second underlayer controls crystal orientation, and the third underlayer further refines grain structure. This segmentation allows each layer to perform its specific function without interfering with the ordering process, thereby improving medium SNR while maintaining crystal grain ordering.
Solution Approach 2:
The patent introduces a second underlayer made of Ru-Al alloy as an intermediary between the first underlayer (CoFeB) and the third underlayer (MgO). This intermediate layer serves as a buffer that controls crystal orientation and promotes uniform grain growth, mediating the interaction between the ordering-promoting first underlayer and the orientation-controlling third underlayer, thus maintaining L10 ordering while improving medium SNR.
2Quantity of substance
If magnetic grain size is reduced to increase recording density, then storage capacity is improved, but exchange coupling between grains increases
Solution Approach 1:
The patent creates different local environments for crystal grain growth by using multiple underlayers with distinct compositions. Each underlayer layer provides specific local conditions (chemical composition, crystal structure, lattice mismatch) that control the size and distribution of magnetic grains in the magnetic layer. This local quality control allows reduction of magnetic grain size for higher recording density while maintaining appropriate exchange coupling through controlled grain boundary characteristics.
3Reliability
If L10 type ordered alloy is used for high perpendicular magnetic anisotropy, then thermal stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary actions during the underlayer formation stage to ensure L10 ordering in the magnetic layer. The first underlayer (CoFeB) is specifically designed and positioned to promote L10 ordering before the magnetic layer is deposited. This preliminary promotion of ordering reduces the need for complex post-deposition heat treatment processes and simplifies manufacturing while ensuring thermal stability through L10 ordered structure.
Solution Approach 2:
The patent controls specific parameters of the underlayer (composition ratios of Co, Fe, B, Ru, Al, Mg, O, thicknesses) to optimize the promotion of L10 ordering. By precisely controlling these parameters during deposition, the patent achieves reliable L10 ordered structure formation without requiring complex manufacturing processes, thus improving thermal stability while keeping manufacturing complexity manageable.
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 proposed solution improves medium SNR and reduces switching field distribution by ensuring uniform crystal grain size and reduced exchange coupling, maintaining high crystal magnetic anisotropy and recording density in magnetic storage apparatuses using heat-assisted or microwave-assisted recording methods.
Implementation Method 1
at least one crystalline underlayer which has a (100) orientation... promotes uniform crystal grain growth
Implementation Method 2
L10 type ordered alloy within the magnetic layer preferably has a good (001) orientation... high perpendicular magnetic anisotropy
Implementation Method 3
the exchange coupling between the magnetic grains is reduced compared to a case in which the grain boundary material is not added
Data Source
AI summary
A magnetic recording medium includes a substrate, a magnetic layer including an alloy having an L10 type crystal structure as a main component thereof, and a plurality of underlayers arranged between the substrate and the magnetic layer. The plurality of underlayers include at least one crystalline underlayer which has a (100) orientation, and includes W as a main component thereof and one or more kinds of elements selected from a group consisting of Fe, Ni, Co, Hf, Zr, Y, Be, Ce, La, and Sc.