Heat-Assisted Magnetic Recording Medium Grain Boundary Segregation
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Solution Overview
Problem
The heat-assisted magnetic recording medium faces challenges in achieving high surface recording density due to issues with grain boundary segregation and heat dissipation, which affect the electromagnetic conversion characteristics when using alloys with the L10 crystal structure.
Innovation Solution
A heat-assisted magnetic recording medium is designed with a substrate, underlayer, and magnetic layers having a granular structure with specific volume fractions of C, SiO2, and BN at grain boundaries, optimizing the volume ratios and thicknesses to enhance grain refinement and heat dissipation, thereby improving electromagnetic conversion characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the content of grain boundary segregation material in the magnetic layer is increased to refine magnetic grains, then the arithmetic average roughness decreases, but the grain boundary segregation material diffuses into magnetic grains and coercivity decreases, deteriorating electromagnetic conversion characteristic
Solution Approach 1:
The patent applies local quality by creating distinct regions within the magnetic layer with different compositions and properties. The magnetic layer is divided into grain interior regions (maintaining high coercivity) and grain boundary regions (providing refinement and low roughness). This is achieved through controlled segregation of specific elements to grain boundaries while maintaining the L10 ordered structure in grain interiors, allowing each region to optimize its local function without compromising the other.
Solution Approach 2:
The patent employs composite materials by combining multiple elements (Fe, Pt, C, Si, B, N) in specific proportions and arrangements. The magnetic layer consists of a Fe-Pt base alloy with L10 structure complemented by grain boundary segregation materials (C, Si, B, N) that form a composite structure. This composite approach allows the system to simultaneously achieve grain refinement, low roughness, and maintained coercivity by distributing different materials to different locations within the layer.
2Reliability
If a high-Ku material with L10 crystal structure is used to maintain thermal stability, then coercivity is maintained, but the electromagnetic conversion characteristic deteriorates due to poor heat dissipation
Solution Approach 1:
The patent applies parameter changes by modifying the magnetic layer composition to include specific elements (C, Si, B, N) in controlled amounts (0.1-5 at% each). These compositional parameter changes alter the thermal conductivity and heat dissipation characteristics of the L10 structured magnetic layer. The addition of these elements changes the physical parameters of the material while maintaining the essential L10 crystal structure and high Ku value, thereby improving heat dissipation without sacrificing thermal stability.
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 optimized structure achieves improved electromagnetic conversion characteristics and heat dissipation, leading to enhanced coercivity and arithmetic average roughness, resulting in better recording density and signal-to-noise ratio.
Implementation Method 1
a material having a high magnetocrystalline anisotropy constant Ku, that is, a high-Ku material, may be used for a magnetic recording layer
Implementation Method 2
the coercivity of the magnetic recording medium is locally reduced
Implementation Method 3
when a content of a grain boundary segregation material in the magnetic layer is small, the magnetic grains cannot be refined, and an arithmetic average roughness of the heat-assisted magnetic recording medium becomes large
Implementation Method 4
The heat-assisted magnetic recording method irradiates near-field light on the magnetic recording medium to locally heat the surface of the magnetic recording medium and assist the recording
Implementation Method 5
if a heat dissipation of the magnetic layer including the alloy having the L10 crystal structure is low, the electromagnetic conversion characteristic of the heat-assisted magnetic recording medium deteriorates
Data Source
AI summary
A heat-assisted magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L10 crystal structure and first and second layers, arranged in this order. Each of the first and second layers has a granular structure including C, SiO2, and BN at grain boundaries. Vol % of the grain boundaries in each of the first and second layers is 25 to 45 vol %. Vol % of C in the first layer is 5 to 22 vol %, and a volume ratio of SiO2 with respect to BN in each of the first and second layers is 0.25 to 3.5. Vol % of SiO2 in the second layer is greater than that of the first layer by 5 vol % or more. Vol % of BN in the second layer is smaller than that in the first layer by 2 vol % or more.