Perpendicular Magnetic Recording Medium Intermediate Layer Design
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Solution Overview
Problem
Conventional perpendicular magnetic recording media face challenges in achieving high-density recording due to incomplete crystal grain boundary formation and excessive exchange interactions between magnetic grains, which affect the magnetization reversal and recording performance.
Innovation Solution
A perpendicular magnetic recording medium is developed with an intermediate layer comprising a CoCr-based alloy and an oxide, where the oxygen content is between 6 at% and 20 at%, forming a granular structure similar to the magnetic recording layer, thereby promoting a continuous crystal grain boundary and reducing exchange interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an intermediate layer is formed to improve crystal orientation of the magnetic recording layer, then crystal orientation is improved, but the exchange interaction between magnetic grains cannot be completely eliminated and magnetization reversal unit becomes larger than average grain size
Solution Approach 1:
The intermediate layer is divided into multiple sub-layers with different materials and functions. The first intermediate layer (Ru-based) provides crystal orientation, while the second intermediate layer (CoCrPt-based with oxide) creates grain boundaries. This segmentation allows each sub-layer to optimize its specific function without interfering with the other, resolving the contradiction between achieving good crystal orientation and preventing excessive exchange interaction.
Solution Approach 2:
The second intermediate layer acts as an intermediary between the first intermediate layer and the magnetic recording layer. It mediates the interaction by providing a CoCrPt-based structure with oxide that promotes grain boundary formation, thereby controlling the exchange interaction between magnetic grains while allowing the first intermediate layer to maintain crystal orientation.
2Productivity
If the magnetic grain size is scaled down to increase recording density, then recording density is improved, but the exchange interaction between grains increases and magnetization reversal becomes less independent
Solution Approach 1:
The patent applies different material compositions and structures to different regions of the intermediate layer. The first intermediate layer has Ru-based composition optimized for crystal orientation, while the second intermediate layer has CoCrPt-based composition with oxide added specifically to promote grain boundary formation. This local quality differentiation allows small grain sizes for high density while maintaining magnetization independence through enhanced grain boundaries in specific regions.
Solution Approach 2:
The intermediate layer structure uses composite materials: Ru-based alloy in the first layer and CoCrPt-based alloy with oxide in the second layer. This composite approach combines the crystal orientation benefits of Ru with the grain boundary formation benefits of CoCrPt and oxide, enabling both high recording density and reliable magnetization reversal independence.
3Stability of the object's composition
If an Ru intermediate layer is formed to improve crystal orientation, then crystal orientation is improved, but the fine structure of the magnetic recording layer changes greatly depending on formation conditions and additional processing is required
Solution Approach 1:
The patent merges the crystal orientation function and the grain boundary control function into a single integrated intermediate layer structure. The CoCrPt-based intermediate layer with added oxide simultaneously provides both crystal orientation improvement and grain boundary formation promotion, eliminating the need for separate Ru layer formation and reducing structural complexity.
Solution Approach 2:
The patent changes the material parameters of the intermediate layer by adding oxide to the CoCrPt-based alloy. This parameter change (adding oxide component) fundamentally alters the intermediate layer's properties to simultaneously achieve crystal orientation and grain boundary formation, simplifying the overall structure compared to multi-layer Ru-based approaches.
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 allows for accurate control of magnetization reversal in small units, enhancing high-density recording capabilities and signal quality while maintaining crystal orientation, leading to improved recording density and thermal stability.
Implementation Method 1
since exchange interactions acting between the magnetic grains separated by the crystal grain boundary is smaller than those acting on the inside of each of the magnetic grains, the magnetic grain is a basic unit for magnetization reversal in magnetic recording
Data Source
AI summary
Embodiments of the present invention help allow accurate control of the magnetization reversal in a magnetic recording layer in small reversal units, whereby high-density recording can be achieved. According to one embodiment, by forming an intermediate layer having a granular structure similar to that of the magnetic recording layer below the magnetic recording layer, a continuous crystal grain boundary is formed at the interface between the magnetic recording layer and the intermediate layer, thereby preventing incomplete formation of the crystal grain boundary found in the initial growth layer of the magnetic recording layer. The intermediate layer comprises a non-magnetic alloy comprising Co and Cr as its main components and an oxide such as Al, Cr, Hf. Mg, Nb, Si, Ta, Ti and Zr. Further, the average content of the oxygen element in the intermediate layer is in the range from 6 at % to 20 at %.