Cubic Ferrite Magnetic Recording Medium for High SNR
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Solution Overview
Problem
Magnetic recording media face challenges in achieving high Signal-Noise Ratio (SNR) due to the decrease in coercive force and increased self-demagnetization when using needle shape magnetic powders for ultrashort wavelength recording, leading to insufficient output and noise.
Innovation Solution
A magnetic recording medium is developed using a cubic crystal ferrite magnetic powder with a specific orientation and composition, including Co, Ni, Mn, Al, and Zn, which provides a sum of squareness ratios in the longitudinal and vertical directions of 1.2 or more and a difference of 0.15 or more, enhancing coercive force and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If needle shape magnetic powders are used for ultrashort wavelength recording, then recording density is improved, but coercive force decreases and self-demagnetization increases
Solution Approach 1:
The invention changes the shape parameter of magnetic particles from needle shape to plate shape with specific aspect ratio (0.5 ≤ LAM/LBM ≤ 2.0), and controls particle size parameters (10 ≤ LAM ≤ 30 nm) to achieve both high recording density and sufficient coercive force. This parameter optimization resolves the contradiction between recording density and coercive force.
Solution Approach 2:
The invention uses composite magnetic layer structure containing plate shape magnetic particles with specific crystal structure (cubic or hexagonal) combined with controlled binder content (3-10 mass%), creating a composite material system that maintains high coercive force while enabling ultrashort wavelength recording.
2Length of moving object
If needle shape magnetic powders are shortened for ultrashort wavelength recording, then recording wavelength is reduced, but output becomes insufficient due to increased self-demagnetization
Solution Approach 1:
The invention transitions from needle shape (high aspect ratio) to plate shape (low aspect ratio 0.5 ≤ LAM/LBM ≤ 2.0) magnetic particles, changing the geometric form to reduce self-demagnetization effects while maintaining appropriate size for ultrashort wavelength recording, thereby preserving sufficient output.
Solution Approach 2:
The invention optimizes particle size parameters (10 ≤ LAM ≤ 30 nm) and aspect ratio (0.5 ≤ LAM/LBM ≤ 2.0) to achieve the right balance between short wavelength capability and maintaining sufficient magnetic moment for adequate output signal.
3Quantity of substance
If hexagonal crystal barium ferrite magnetic powder is used for high density recording, then recording density is improved, but manufacturing complexity increases
Solution Approach 1:
The invention specifies particular crystal structures (cubic or hexagonal) and compositional ranges for magnetic particles to achieve high density recording while maintaining manufacturability through well-established material systems with controllable properties.
Solution Approach 2:
The invention defines specific parameter ranges (particle size 10-30 nm, aspect ratio 0.5-2.0, binder content 3-10 mass%) that balance high recording density with manufacturability, using material systems that can be produced with existing technology.
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 solution results in a magnetic recording medium with improved SNR and capability for short wavelength recording, achieving low direct current erasing noise and high output.
Implementation Method 1
The needle shape magnetic powders are magnetized in the longitudinal direction thereof during the formation of the magnetic layer
Implementation Method 2
a sum of a squareness ratio in a longitudinal direction and a squareness ratio in a vertical direction is 1.2 or more
Data Source
AI summary
The magnetic recording medium includes a long substrate body, and a magnetic layer including a powder of cubic crystal ferrite magnetic particles. The sum of a squareness ratio in the longitudinal direction and a squareness ratio in the vertical direction is 1.2 or more, and the difference of the squareness ratio in the longitudinal direction and the squareness ratio in the vertical direction is 0.15 or more.