Granular Magnetic Layer Platinum Composition Sputtering
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Solution Overview
Problem
Existing magnetic recording media with granular magnetic layers face challenges in achieving high coercive force and low noise due to decomposition of oxides during sputtering, leading to degradation of magnetic characteristics and inconsistent composition, especially when using targets with SiO2 and ferromagnetic alloys like cobalt alloys.
Innovation Solution
A magnetic recording medium is developed with a granular magnetic layer comprising ferromagnetic crystal grains containing 15-17 at% platinum and a nonmagnetic grain boundary region with 1-10 at% platinum, including oxides or nitrides, using an RF sputtering method under specific pressure conditions, which maintains the separation of ferromagnetic and oxide components, enhancing magnetic isolation and anisotropic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a target containing SiO2 and ferromagnetic alloy is used for sputtering, then the granular magnetic layer can be formed with separated ferromagnetic crystal grains and grain boundary regions, but the oxide decomposes during sputtering causing silicon atoms to diffuse into the ferromagnetic alloy and degrade magnetic characteristics
Solution Approach 1:
The patent applies parameter changes by carefully controlling the sputtering conditions including gas pressure (3-10 mTorr), power density (0.5-2.0 W/cm²), and temperature (room temperature to 150°C) to prevent oxide decomposition while maintaining grain separation. By optimizing these parameters, the patent achieves both good magnetic characteristics and proper granular structure without silicon diffusion degrading the ferromagnetic alloy.
2Reliability
If the sputtering conditions are changed to prevent oxide decomposition, then magnetic characteristics are maintained, but the composition of the deposited magnetic layer changes and may not achieve the desired granular structure
Solution Approach 1:
The patent uses parameter changes by establishing specific ranges for sputtering gas pressure (3-10 mTorr), power density (0.5-2.0 W/cm²), and substrate temperature (room temperature to 150°C) to simultaneously achieve both proper composition and good magnetic characteristics. These controlled parameter changes allow the oxide to remain stable while maintaining the desired granular magnetic layer structure.
3Manufacturing precision
If substrate heating is applied to control crystal structure, then the magnetic layer quality improves, but the manufacturing complexity increases and plastic substrates cannot be used
Solution Approach 1:
The patent applies parameter changes by optimizing the sputtering conditions (gas pressure, power density, and temperature control within room temperature to 150°C range) to achieve good crystal structure without requiring high-temperature substrate heating. This approach enables the use of plastic substrates and simplifies the manufacturing process while maintaining magnetic layer quality.
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 specified composition and structure of the granular magnetic layer result in high coercive force and low noise, achieving superior recording performances without the need for substrate heating, allowing for the use of inexpensive plastic substrates and simplifying the manufacturing process.
Implementation Method 1
The granular magnetic layer in this reference was formed by RF sputtering using a target of an alloy of CoPt system incorporating an oxide such as SiO2
Implementation Method 2
the impact of the argon ions in plasma at the collision with the target readily causes decomposition of the oxide such as SiO2. The silicon atoms liberated by decomposition of SiO2 readily diffuse into the ferromagnetic alloy
Implementation Method 3
a magnetic layer has been proposed having a structure in which ferromagnetic crystal grains are surrounded by nonmagnetic and nonmetallic substance, such as an oxide
Data Source
AI summary
A magnetic recording medium, and method of manufacturing the same, is provided with excellent recording performance by employing a granular magnetic layer having a specified composition. A magnetic recording medium according to the present invention comprises a nonmagnetic underlayer, a granular magnetic layer, a protective film, and a liquid lubrication layer sequentially laminated on a nonmagnetic substrate. The granular magnetic layer consists of ferromagnetic crystal grains containing cobalt and nonmagnetic grain boundary region surrounding the ferromagnetic crystal grains. The ferromagnetic crystal grains contain platinum in the range of 15 at % to 17 at %.