Graded MgO Under-layer for FePt Crystal Orientation
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Solution Overview
Problem
Magnetic recording media with L10-ordered FePt alloy faces challenges in achieving high surface recording density while maintaining thermal stability, with issues of surface roughness and corrosion resistance, particularly due to the need for (001) crystal orientation and the degradation of flyability characteristics over time.
Innovation Solution
A magnetic recording medium is designed with a layered structure including a buffer layer, a first MgO under-layer with lower oxygen concentration, and a second MgO under-layer with higher oxygen concentration, reducing surface roughness and improving corrosion resistance and crystal orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a MgO under-layer is used to achieve (001) crystal orientation of FePt layer, then crystal orientation is improved, but surface roughness is enhanced and corrosion resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating a MgO under-layer with non-uniform oxygen concentration distribution. The oxygen concentration is higher near the FePt interface and lower toward the buffer layer, forming distinct regions within the same layer. This gradient structure provides (001) crystal orientation promotion at the FePt interface while maintaining smooth surface characteristics away from the interface, thereby resolving the contradiction between crystal orientation and surface roughness.
2Strength
If heating to at least 300° C. is performed to achieve L10 ordering and (001) crystal orientation, then magnetic anisotropy energy is improved, but thermal stability and material integrity may be compromised
Solution Approach 1:
The patent changes the physical-chemical parameters of the MgO under-layer by controlling oxygen concentration distribution. This parameter modification enables the FePt layer to achieve L10 ordering and (001) crystal orientation at lower temperatures or with reduced thermal stress, thereby improving magnetic anisotropy energy while maintaining thermal stability and preventing material degradation.
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 improved under-layer structure enhances crystal orientation, reduces surface roughness, and maintains excellent flyability characteristics over a long period, addressing the challenges of corrosion resistance and thermal stability in magnetic recording media.
Implementation Method 1
it is widely known that (001) crystal orientation can be performed by employing a suitable material as the under-layer formed below the FePt layer. Laid-open Japanese Patent Application Number 2012-48784 discloses an FePt layer having (001) crystal orientation, due to the use of a MgO under-layer.
Implementation Method 2
A magnetic medium is described for perpendicular magnetic data recording that includes an under-layer and a magnetic recording layer formed over the under-layer
Data Source
AI summary
A magnetic medium for perpendicular magnetic data recording having improved corrosion characteristics and reduced surface roughness. The magnetic medium includes an under-layer and a perpendicular magnetic recording layer formed over the under-layer. The under-layer can be formed of MgO and has an oxygen concentration that is greater at the perpendicular magnetic recording layer than it is away from the perpendicular magnetic recording layer.