Magnetic Recording Medium Underlayer Structure for Surface Smoothness
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Solution Overview
Problem
The existing magnetic recording media with L10 structure alloys suffer from decreased surface smoothness and increased waviness due to lattice distortion and imperfect laminate structures of underlayers, which affect the recording density and signal-to-noise ratio.
Innovation Solution
A magnetic recording medium with a specific layered structure comprising a substrate, underlayers, and a magnetic layer, where the underlayers include Mo and Ru with controlled Ru content, and additional elements for improved lattice matching, and a magnetic layer with a FePt or CoPt alloy, along with additional materials for enhanced magnetocrystalline anisotropy, to reduce lattice distortion and maintain surface smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heating is performed during the formation of underlayers and prior to the formation of the magnetic layer to achieve high c-axis orientation of the L10 structure alloy, then the magnetocrystalline anisotropy and coercivity are improved, but the surface smoothness decreases and waviness increases due to lattice distortion
Solution Approach 1:
The underlayer is divided into multiple layers with different materials (Cr, W, Mo, Ru, Rh, Ir) to achieve both high c-axis orientation and maintain surface smoothness. Each layer contributes differently to the overall structure, with some layers promoting crystalline orientation while others maintain surface quality.
Solution Approach 2:
The underlayer uses composite material structures combining BCC structure materials (Cr, W, Mo) with other elements (Ru, Rh, Ir) to achieve both high c-axis orientation and reduced lattice distortion. The composite structure allows synergistic effects where different materials compensate for each other's weaknesses.
2Reliability
If a laminate structure of multiple underlayers is used to improve lattice matching with the L10 structure magnetic layer, then the coercivity and thermal stability are enhanced, but the surface smoothness decreases due to imperfect laminate structure and lattice distortion
Solution Approach 1:
The underlayer is segmented into multiple functional layers (Cr layer, W layer, Mo layer, Ru layer, Rh layer, Ir layer) where each layer serves specific purposes. This segmentation allows optimization of each layer's properties to collectively achieve both thermal stability and surface smoothness.
Solution Approach 2:
Different regions of the underlayer structure have different material compositions and properties optimized for specific functions. For example, certain layers are optimized for lattice matching while others are optimized for surface smoothness, creating local quality variations that collectively solve the contradiction.
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 structure enhances surface smoothness, reduces waviness, and increases the signal-to-noise ratio and areal recording density by improving lattice matching and crystallinity, allowing for more efficient data recording.
Implementation Method 1
lattice matching between the materials having the BCC structure and the NaCl-type structure, which have a (100) orientation, and the material having the L10 structure, which has a (001) orientation, is high
Implementation Method 2
heating during the formation of the underlayers and heating prior to the formation of the magnetic layer cause the surface smoothness of the magnetic recording medium to decreases and the waviness to increase
Data Source
AI summary
A magnetic recording medium includes a substrate, an underlayer formed on the substrate, and a magnetic layer formed on the underlayer. The magnetic layer includes an alloy having a L10 structure. The underlayer includes a first underlayer and a second underlayer. The first underlayer includes Mo and Ru, the content of Ru in the first underlayer is in a range of 5 atom % to 30 atom %, and the second underlayer includes a material having a body-centered cubic (BCC) structure. The second underlayer is formed between the first underlayer and the substrate.