Core-Shell Magnetic Particle Exchange Coupling
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Solution Overview
Problem
Magnetic recording media face challenges in achieving both high thermal stability and suitable recording properties, particularly with the use of rare earth elements, as high crystal magnetic anisotropy materials require large external magnetic fields and are difficult to apply to nonmagnetic organic supports due to heat resistance issues.
Innovation Solution
A method involving the attachment of a transition metal-containing organic compound to the surface of hard magnetic particles, followed by thermal decomposition, creates a core/shell structure with a soft magnetic shell that exchange-couples with the hard magnetic core, reducing the switching field and maintaining thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high crystal magnetic anisotropy materials (e.g., rare earth elements like SmCo, NdFeB) are used to achieve thermal stability, then thermal stability is improved, but the switching magnetic field increases requiring large external magnetic fields for recording
Solution Approach 1:
The magnetic particle is segmented into a core-shell structure where the core contains the hard magnetic material (rare earth element-based) providing thermal stability, and the shell contains a soft magnetic material reducing the switching field. This segmentation allows each part to fulfill its specific function independently, resolving the contradiction between thermal stability and recording properties
Solution Approach 2:
The invention uses composite materials by combining hard magnetic material (for thermal stability) and soft magnetic material (for reduced switching field) into a single magnetic particle. The core-shell composite structure enables the particle to simultaneously exhibit high thermal stability from the core and suitable recording properties from the shell, resolving the technical contradiction
2Reliability
If gas phase film formation is used to create exchange coupling between soft and hard magnetic layers, then recording properties are improved, but high temperatures are required that are incompatible with organic material supports
Solution Approach 1:
The soft magnetic shell is formed on the hard magnetic core through preliminary action (attachment of transition metal-containing organic compound followed by thermal decomposition at moderate temperatures) before the magnetic particle is incorporated into the organic support. This preliminary formation of the exchange-coupled structure avoids the need for high-temperature processing after support integration, making the process compatible with heat-sensitive organic materials
Solution Approach 2:
The invention changes the processing temperature parameter from high temperatures (required for gas phase film formation) to moderate temperatures (suitable for organic support processing). By using wet chemical methods and controlled thermal decomposition at lower temperatures, the exchange coupling is achieved without damaging the organic support, resolving the temperature contradiction
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 approach allows for magnetic particles with both high thermal stability and coercive force suited to recording, enabling their use in particulate magnetic recording media without the need for high-temperature processing on organic supports.
Implementation Method 1
thermally decomposing the transition metal-containing organic compound
Implementation Method 2
produce exchange coupling interaction
Data Source
AI summary
An aspect of the present invention relates to a method of preparing a magnetic particle, which comprises attaching a transition metal-containing organic compound to a surface of a hard magnetic particle and then thermally decomposing the transition metal-containing organic compound to obtain the magnetic particle.