Sm-Fe-N Magnet with Soft Magnetic Binder for Exchange Interaction Stability
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Solution Overview
Problem
Sm—Fe—N-based composite magnets produced by existing methods often have coercive force Hc lower than expected due to instability in the exchange interaction between soft and hard magnetic phases, affecting reproducibility of magnetic properties.
Innovation Solution
A magnet is created with hard magnetic particles containing rare-earth metals and a soft magnetic material interposed between them to ensure stable exchange interaction, achieved through a process involving dispersion liquid preparation, recovery, molding, and sintering, with specific particle size and volume ratio controls to optimize inter-particle distances and binding effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Sm—Fe—N-based composite magnets are produced by existing methods with uniform particle sizes, then particle size uniformity is achieved, but coercive force Hc is lower than expected due to instability in exchange interaction
Solution Approach 1:
The patent changes the particle size parameter to resolve the contradiction. Specifically, it sets the hard magnetic particle size to 100 nm or more and the soft magnetic particle size to smaller than the hard magnetic particles, creating an optimal size relationship that ensures stable exchange interaction. This parameter optimization achieves both particle size uniformity and high coercive force stability by preventing premature aggregation while maintaining exchange coupling.
2Quantity of substance
If soft and hard magnetic phases are made to coexist in fine sizes for exchange interaction, then residual magnetization Br is improved, but coercive force Hc becomes unstable
Solution Approach 1:
The patent applies local quality by creating distinct regions with different magnetic properties. Hard magnetic particles (100 nm or more) provide high coercive force, while softer magnetic particles (smaller size) provide high residual magnetization. The controlled size distribution and inter-particle spacing ensure that each particle type maintains its local magnetic characteristics while contributing to the overall composite performance, achieving both high Br and stable Hc.
3Reliability
If hard magnetic particles are used with average particle size of 100 nm or more, then exchange interaction stability is improved, but particle size control becomes more challenging
Solution Approach 1:
The patent employs preliminary action by pre-controlling the particle size of hard magnetic particles to be 100 nm or more before assembling the composite structure. This pre-establishment of optimal particle dimensions ensures that exchange interaction stability is achieved from the outset, while the subsequent formation of the composite with softer magnetic particles maintains this stability without requiring further complex size adjustments.
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 magnets with enhanced stability and magnetic properties, achieving high residual magnetization and coercive force, thereby improving the energy product (BH)max and ensuring consistent magnetic behavior.
Implementation Method 1
a soft magnetic phase having high residual magnetization Br and a hard magnetic phase having high coercive force Hc are made to coexist in fine sizes of several tens of nanometers or less such that exchange interaction occurs, to thereby provide a nanocomposite magnetic material in which the two phases are magnetically coupled
Implementation Method 2
a step of sintering the molded mixture body
Data Source
AI summary
A magnet includes hard magnetic particles containing a rare-earth metal, and a soft magnetic material interposed between the hard magnetic particles to bind together the hard magnetic particles.