Perpendicular Magnetic Recording Medium Two-Layer Grain Structure
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Solution Overview
Problem
In perpendicular magnetic recording media, achieving high recording density requires improving coercive force (Hc) while maintaining a high Signal-Noise Ratio (SNR), but increasing film thickness to enhance Hc often degrades SNR.
Innovation Solution
A two-layer magnetic recording structure is implemented, with the first layer having finer crystal grains and improved orientation, and the second layer having larger grains, where the average particle diameter ratio of the first to the second layer is 0.8<A/B<1, using non-magnetic substances like chrome, oxygen, or oxides to form grain boundaries, optimizing SNR and coercive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the film thickness of the magnetic recording layer is increased to improve coercive force Hc, then the coercive force Hc is improved, but the Signal-Noise Ratio (SNR) is decreased
Solution Approach 1:
The magnetic recording layer is divided into two distinct layers: a first magnetic recording layer with finer crystal grains (smaller particle diameter) and a second magnetic recording layer with coarser crystal grains (larger particle diameter). This segmentation allows each layer to contribute differently to the overall performance, with the first layer providing higher coercive force and the second layer providing better SNR, thereby resolving the contradiction between improving Hc and maintaining SNR.
Solution Approach 2:
Different regions of the magnetic recording structure are given different properties: the first magnetic recording layer has finer grains optimized for high coercive force, while the second magnetic recording layer has coarser grains optimized for high SNR. This local differentiation of grain size and magnetic properties allows simultaneous optimization of both contradictory parameters without requiring a uniform structure throughout.
2Reliability
If a two-layer magnetic recording structure is used to improve both coercive force and SNR by controlling grain size, then the structure complexity increases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for controlling the crystal grain particle diameters: the first magnetic recording layer has particle diameter of 5-15 nm, the second layer has 15-30 nm, with their ratio A/B satisfying 0.7 < A/B < 0.95. By defining these specific parameter ranges and ratios, the invention transforms the manufacturing challenge into a controllable parameter optimization problem, where precise control within specified ranges achieves the desired performance without requiring extreme precision.
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 structure enhances SNR while maintaining a high coercive force, achieving optimal recording density by controlling grain size and orientation in the magnetic recording layers.
Implementation Method 1
a first magnetic recording layer and a second magnetic recording layer which are ferromagnetic layers of a granular structure in which non-magnetic grain boundary parts are formed between crystal grains
Data Source
AI summary
A perpendicular magnetic recording medium 100 having a magnetic recording layer 122, wherein a particle diameter of crystal grains in layer 122 improves a SNR while a high coercive force is maintained. There also is at least a ground layer 118, a first magnetic recording layer 122a, and a second magnetic recording layer 122b in this order on a disk base 110. The first layer 122a and the second 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 columnar shape, and A<B when an average particle diameter of the crystal grains in the first magnetic recording layer 122a is taken as A nm and an average particle diameter of the crystal grains in the second magnetic recording layer 122b is taken as B nm.