Perpendicular Magnetic Recording Medium Multilayer Structure
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Solution Overview
Problem
Conventional perpendicular magnetic recording media face challenges in achieving a sufficient thickness while maintaining high magnetic anisotropy, particularly with monolayer configurations of ordered alloy-nonmagnetic material combinations, which lead to secondary growth and decreased magnetic anisotropy.
Innovation Solution
A magnetic recording medium is developed with a multilayer structure, where the first magnetic recording layer is formed using an ordered alloy like FePt-C and the second layer incorporates a carbon-containing nonmagnetic material such as FePt-B4C or FePt-SiC, with the nonmagnetic crystal grain boundary composed of carbides or carbon and boron/silicon, allowing for increased film thickness while preserving high magnetic anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the magnetic recording layer is increased in a monolayer configuration, then the recording capacity is improved, but secondary growth occurs and magnetic anisotropy decreases
Solution Approach 1:
The magnetic recording layer is divided into multiple sub-layers (first magnetic recording layer and second magnetic recording layer) with different nonmagnetic materials. This segmentation allows each layer to have optimized properties: the first layer uses carbon for fine grain boundaries, while the second layer uses carbides or carbon-boron/silicon combinations for enhanced grain boundary strength without causing secondary growth, thereby maintaining magnetic anisotropy even at increased total thickness.
Solution Approach 2:
The invention employs composite material structures where different nonmagnetic materials (carbon, carbides, carbon-boron, carbon-silicon) are combined in specific layers. This composite approach leverages the advantages of each material: carbon provides fine grain separation, while carbides and carbon-boron/silicon combinations provide stronger grain boundaries that prevent secondary growth, enabling thicker films with maintained magnetic anisotropy.
2Manufacturing precision
If carbon is used as the nonmagnetic material in the magnetic recording layer, then fine crystal grain structure is achieved, but grain boundary strength is insufficient leading to secondary growth
Solution Approach 1:
Different nonmagnetic materials are selectively applied to different layers based on local requirements. The first magnetic recording layer uses carbon to achieve fine crystal grain structure, while the second magnetic recording layer uses carbides or carbon-boron/silicon combinations to provide stronger grain boundaries. This local quality differentiation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The invention creates a composite structure where carbon is combined with other elements (boron, silicon) or compounds (carbides) in the second layer. This composite material approach enhances grain boundary strength while maintaining the fine crystal grain structure achieved by carbon, preventing secondary growth through the synergistic effect of multiple materials.
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 enables the attainment of a predetermined film thickness with maintained high magnetic anisotropy, improving the recording density and thermal stability of the magnetic recording medium.
Implementation Method 1
The granular magnetic material is constituted by a magnetic material and a nonmagnetic material and has a granular structure constituted by magnetic crystal grains and a nonmagnetic material that has precipitated such as to surround the periphery of the magnetic crystal grains
Implementation Method 2
ordered alloys have attracted attention as the magnetic materials, and carbon based, oxide base, and nitride based materials are known as the nonmagnetic material
Implementation Method 3
high magnetic anisotropy is maintained
Data Source
AI summary
A perpendicular magnetic recording medium includes at least a nonmagnetic substrate and a magnetic recording layer. The magnetic recording layer is constituted by a plurality of layers that includes at least a first magnetic recording layer and a second magnetic recording layer. The first magnetic recording layer has a granular structure that includes first magnetic crystal grains and first nonmagnetic crystal grain boundaries surrounding the first magnetic crystal grains. The first magnetic crystal grains include an ordered alloy, and the first nonmagnetic crystal grain boundaries are constituted by carbon. The second magnetic recording layer has a granular structure that includes second magnetic crystal grains and a second nonmagnetic crystal grain boundaries that surround the second magnetic crystal grains. The second magnetic crystal grains include an ordered alloy, and the second nonmagnetic crystal grain boundaries are constituted by a carbon-containing nonmagnetic material.