Hexagonal Ferrite Powder for High-Density Magnetic Recording
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Solution Overview
Problem
Conventional methods struggle to simultaneously reduce the particle size of hexagonal ferrite powder, increase its saturation magnetization, and enhance the coating durability of magnetic layers in magnetic recording media, while maintaining high magnetic stability and thermal stability.
Innovation Solution
Development of hexagonal ferrite powder with an average particle size of 10-35 nm, comprising at least 70% isotropic particles with a major axis to minor axis ratio less than 2.0, achieving a saturation magnetization of 30 A·m2/kg or higher, and employing a continuous hydrothermal synthesis method to control particle shape and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the particle size of hexagonal ferrite powder is reduced to increase fill rate and decrease noise, then the coating durability of the magnetic layer deteriorates
Solution Approach 1:
The patent changes the particle size parameters to a specific range (10-35 nm average diameter) and controls the shape anisotropy parameters to achieve both high fill rate and adequate coating durability. This parameter optimization resolves the contradiction between reducing particle size for noise reduction and maintaining coating durability.
Solution Approach 2:
The patent develops a composite magnetic layer containing hexagonal ferrite particles with specific properties (small size, high saturation magnetization, controlled shape) combined with binder materials. This composite structure achieves high fill rate while maintaining coating durability through the synergistic properties of the composite system.
2Manufacturing precision
If organic molecules are placed in hydrothermal synthesis reaction to control particle size, then the saturation magnetization is reduced
Solution Approach 1:
The patent modifies the hydrothermal synthesis parameters by controlling temperature (200-400°C), pressure, reaction time, and the type/amount of organic molecules used. These parameter optimizations allow precise particle size control while minimizing the negative impact on saturation magnetization, achieving both small uniform particles and high magnetic properties.
Solution Approach 2:
The patent applies local quality control by using organic molecules selectively during specific stages of synthesis to control particle size and shape in specific regions, while maintaining the bulk magnetic properties. The organic additives are used in controlled amounts and at controlled concentrations to achieve local particle size control without globally reducing saturation magnetization.
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 resulting hexagonal ferrite powder enables high coating durability and improved magnetic characteristics, including enhanced saturation magnetization and thermal stability, suitable for high-density magnetic recording applications.
Implementation Method 1
converting the hexagonal ferrite precursor into hexagonal ferrite by a continuous hydrothermal synthesis method
Data Source
AI summary
An aspect of the present invention relates to hexagonal ferrite powder, which comprises equal to or more than 70% on a particle number basis of isotropic hexagonal ferrite particles satisfying equation (1):major axis length/minor axis length<2.0 (1),having an average particle size of equal to or greater than 10.0 nm but equal to or less than 35.0 nm, and having a saturation magnetization of equal to or greater than 30 A·m2/kg.