Interlayer Structure for Heat-Assisted Magnetic Recording
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Solution Overview
Problem
Magnetic recording media face challenges in achieving high areal density due to thermal stability limits of small magnetic grains, which require materials with high magnetic anisotropy, necessitating energy assistance for writing data, such as heat-assisted magnetic recording (HAMR) that demands specific interlayer structures for orientation, topography, and thermal management.
Innovation Solution
A magnetic stack with an interlayer structure that includes a primary phase with a small grain microstructure and a secondary segregant phase, providing controlled grain orientation, separation, and thermal management, allowing for coherent growth of vertically contiguous two-phase layers to enhance magnetic recording layer properties, including thermal conductivity and diffusion control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If small magnetic grains are used to increase areal density, then recording density is improved, but thermal stability deteriorates due to thermal fluctuations causing magnetization reversal
Solution Approach 1:
The patent employs a composite interlayer structure consisting of multiple layers with different materials (Ru, Rh, Ir, Pt, Pd, Cu, Ag, Au, Al, and their alloys or compounds) to achieve both small grain size for high density and thermal stability. The composite structure allows combining materials with different properties to simultaneously address density and stability requirements
Solution Approach 2:
The patent changes physical and chemical parameters of the interlayer structure, including layer thicknesses (ranging from nanometer to micrometer scales), material composition ratios, and crystalline orientations, to optimize both grain size for high density and thermal stability properties
2Reliability
If materials with high magnetic anisotropy are used to increase thermal stability, then thermal stability is improved, but writing difficulty increases requiring energy assistance
Solution Approach 1:
The patent applies local quality by creating spatially varying properties within the interlayer structure, including localized material compositions and thickness variations that create favorable local magnetic anisotropy conditions in the recording layer while maintaining overall thermal stability through the composite interlayer structure
Solution Approach 2:
The interlayer structure acts as an intermediary between the substrate and the high anisotropy recording layer, providing a template that controls grain nucleation and growth to achieve the desired magnetic properties with reduced writing field requirements
3Reliability
If crystalline grain orientation is controlled to achieve preferred magnetization axes, then magnetic properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating orientation-control mechanisms directly into the interlayer structure during fabrication, such as pre-aligned crystalline layers and epitaxial relationships that automatically guide the formation of preferred magnetization axes in subsequent recording layers, eliminating the need for post-fabrication orientation adjustments
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 interlayer structure enhances thermal stability and recording density by maintaining small grain sizes and preferred magnetization axes, enabling efficient data writing in high anisotropy materials while reducing the need for excessive energy assistance.
Implementation Method 1
The interlayer structure comprises a first layer having cubic crystal structure including <100> oriented crystalline grains and a second layer having crystalline grains laterally separated by a segregant material disposed at grain boundaries of the second layer crystalline grains
Implementation Method 2
Higher areal density for magnetic recording can be achieved by decreasing the size of magnetic grains used for magnetic recording media. As grain sizes with a given magnetic anisotropy energy decrease in volume, eventually a thermal stability limit is reached
Implementation Method 3
Magnetic recording media face challenges in achieving high areal density due to thermal stability limits of small magnetic grains, which require materials with high magnetic anisotropy
Data Source
AI summary
A magnetic stack includes a interlayer structure and a magnetic recording layer disposed over the interlayer in the magnetic stack. The magnetic recording layer includes substantially ordered L10, <001> oriented crystalline magnetic grains laterally separated by a nonmagnetic, segregant material. The interlayer structure comprises a first layer having cubic crystal structure including <100> oriented crystalline grains and a second layer having crystalline grains laterally separated by a segregant material. The crystalline grains of the second layer are arranged in substantially vertically contiguous alignment with the crystalline grains of the first layer and the segregant material of the magnetic recording layer is arranged in substantially vertically contiguous alignment with the segregant material of the second layer.