Perpendicular Magnetic Recording Media Cap Layer Gradient
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Solution Overview
Problem
Conventional magnetic recording media face challenges in achieving higher recording density while maintaining head flyability due to the trade-off between magnetic cluster size and surface roughness, leading to increased inter-granular exchange coupling and reduced cluster size effectiveness.
Innovation Solution
A perpendicular magnetic recording medium with a ferromagnetic granular layer and a cap layer, where the grain diameter decreases and grain boundary oxide width increases near the cap layer, along with a domed shape and oxide-filled indentations, and a nonmagnetic switching control layer to control exchange coupling, resulting in smaller magnetic clusters and reduced surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the cap layer is reduced to decrease magnetic cluster size, then recording density is improved, but surface roughness increases and flyability deteriorates
Solution Approach 1:
The patent applies local quality by creating a gradient in oxide concentration within the granular layer, with higher oxide content near the cap layer interface and lower oxide content deeper in the layer. This localized variation in composition allows the upper region to provide smooth surface contact for flyability while the overall structure maintains small magnetic cluster sizes for high recording density.
2Manufacturing precision
If oxide is reduced in the top part of granular layer to reduce cap layer thickness, then magnetic cluster size is decreased, but inter-granular exchange coupling increases
Solution Approach 1:
The patent employs parameter changes by systematically varying the oxide concentration as a gradient through the depth of the granular layer. By controlling the oxide content to increase toward the cap layer interface, the invention optimizes both magnetic cluster size and inter-granular exchange coupling, achieving small clusters while maintaining stable magnetic properties through the compositional gradient.
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 enhances writability and flyability, allowing for smaller magnetic clusters and improved recording density with reduced surface roughness, effectively addressing the limitations of conventional products.
Implementation Method 1
the strong lateral exchange coupling of the cap layer, the magnetic cluster size in the recording layer constituted as a combination of the granular layer and a cap layer being larger than the cluster size in the granular layer section
Implementation Method 2
a ferromagnetic granular layer with perpendicular magnetic anisotropy and having a granular structure
Data Source
AI summary
In one general embodiment, a perpendicular magnetic recording medium includes a ferromagnetic granular layer with perpendicular magnetic anisotropy and having a granular structure; and a cap layer above said granular layer, the cap layer being a ferromagnetic continuous layer with perpendicular magnetic anisotropy, wherein, near a first side of said granular layer nearest the cap layer. Surfaces of the ferromagnetic grains of said granular layer facing the cap layer each have a domed shape defining undulations along the first side. Indentations in said ferromagnetic grains are filled by the oxide of the grain boundary in a vicinity of the first side of said granular layer. Undulations on a granular layer side of said cap layer are flatter than the undulations of the ferromagnetic grains on the first side of said granular layer.