Perpendicular Magnetic Recording Medium Segmentation
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Solution Overview
Problem
Conventional perpendicular magnetic recording media face challenges in achieving high recording density and overwrite characteristics due to noise increase from the continuous layer positioned above the magnetic recording layer, and the magnetic field strength decreases with distance from the recording head.
Innovation Solution
The structure includes a first magnetic recording layer with intergranular distances between crystal grains of 1 nm or less, allowing it to function similarly to a continuous layer, and a second magnetic recording layer with intergranular distances of 0.5 nm or more, optimizing coercive force and signal-to-noise ratio (SNR), while maintaining a granular structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a continuous layer is provided above the magnetic recording layer to improve overwrite characteristic, then the inverted-magnetic-domain nucleation magnetic field is enhanced, but noise increases due to the continuous layer's position near the reproducing head
Solution Approach 1:
The magnetic recording layer is divided into two distinct layers: a first magnetic recording layer with small intergranular distance (≤1 nm) that functions as a continuous layer for improving overwrite characteristic, and a second magnetic recording layer with larger intergranular distance (≥0.5 nm) that maintains high SNR. This segmentation allows each layer to perform its specific function without the harmful effects of a single continuous layer positioned near the reproducing head.
Solution Approach 2:
Different regions of the magnetic recording medium are given different properties: the first magnetic recording layer has small intergranular distance to provide continuous layer functionality for overwrite improvement, while the second magnetic recording layer has larger intergranular distance to maintain high SNR. This local differentiation resolves the contradiction by assigning different functional characteristics to different parts of the same structure.
2Reliability
If the magnetic field strength is increased to improve recording density, then thermal fluctuation is suppressed, but leakage magnetic field to adjacent tracks increases causing WATE
Solution Approach 1:
The magnetic recording layer is segmented into two layers with different intergranular distances. The first layer with small intergranular distance provides the necessary magnetic field strength for high recording density while the second layer with larger intergranular distance helps confine the magnetic field, reducing leakage to adjacent tracks and minimizing WATE effects.
3Reliability
If intergranular distance is reduced to ≤1 nm in the first magnetic recording layer to enable continuous layer function, then overwrite characteristic is improved, but manufacturing precision requirements increase
Solution Approach 1:
By segmenting the magnetic recording layer into two distinct layers with different intergranular distance requirements, the patent reduces the manufacturing precision burden on the overall structure. The first layer's small intergranular distance (≤1 nm) is optimized for overwrite characteristic, while the second layer's larger intergranular distance (≥0.5 nm) provides a more forgiving manufacturing window, thereby reducing the overall precision requirement compared to a single continuous layer approach.
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 the inverted-magnetic-domain nucleation magnetic field, improves heat-resistant fluctuation characteristics, and optimally improves the overwrite characteristic while maintaining high SNR and coercive force.
Implementation Method 1
a thin film (continuous layer) is formed that shows a high perpendicular magnetic anisotropy above or below the magnetic recording layer having a granular structure
Implementation Method 2
a magnetic field in a direction perpendicular to the magnetic recording layer
Implementation Method 3
the axis of easy magnetization is adjusted so as to be oriented in a direction perpendicular to the base surface
Implementation Method 4
a soft magnetic layer is provided under a magnetic recording layer of a perpendicular magnetic recording disk to form a path (magnetic path) for a magnetic flux
Implementation Method 5
Cr and SiO2 (or TiO2) are subjected to segregation to form a non-magnetic grain boundary
Data Source
AI summary
An object of the present invention is to provide a perpendicular magnetic recording medium in which each space between crystal grains of a first magnetic recording layer is so designed as to allow the layer to also have a function as a continuous layer, and a method of manufacturing a perpendicular magnetic recording medium. In a perpendicular magnetic recording medium 100 according to the present invention, a first magnetic recording layer 122a and a second magnetic recording layer 122b are ferromagnetic layers each having a granular structure in which a grain boundary part made of a non-magnetic substance is formed between crystal grains each grown in a column shape and, in the first magnetic recording layer 122a, an intergranular distance defined by an average of shortest distances between grain boundary parts each between a crystal grain and its adjacent crystal grain is equal to or shorter than 1 nm.