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Updated: Dec 11, 2025
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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
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Magnetic Phase Coexistence and Hard-Soft Exchange Coupling in FePt Nanocomposite Magnets
Nanomaterials (Basel, Switzerland)
|August 23, 2020
Summary
Highly coercive FePt nanocomposite magnets were achieved by annealing FePt alloys at 400°C, forming coexisting hard (L1₀) and soft (L1₂) magnetic phases. This method offers a promising route to rare-earth-free permanent magnets.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Developing rare-earth-free permanent magnets is crucial for sustainable technology.
- FePt alloys are promising for permanent magnets due to their hard magnetic L1₀ phase.
Purpose of the Study:
- To demonstrate phase coexistence in FePt nanocomposite magnets.
- To obtain highly coercive FePt magnets through controlled annealing.
- To explore rare-earth-free permanent magnet alternatives.
Main Methods:
- Preparation of Fe₅₃Pt₄7 and Fe₅₅Pt₄5 alloys via dynamic rotation switching and ball milling.
- Annealing treatments at 400°C and 550°C.
- Structural and magnetic characterization using X-ray diffraction, ⁵⁷Fe Mössbauer spectrometry, and SQUID magnetometry.
Main Results:
- Formation of a predominant, highly ordered L1₀ phase coexisting with a soft L1₂ phase at annealing temperatures as low as 400°C.
- Evidence of phase coexistence confirmed by multiple characterization techniques.
- Achieved high coercivity and remanence, with hysteresis loops showing inflection points indicative of phase coexistence.
Conclusions:
- Successful demonstration of hard-soft magnetic phase coexistence in FePt nanocomposites at low annealing temperatures.
- Optimized annealing leads to enhanced coercivity and energy products comparable to current permanent magnets.
- This approach provides a viable method for fabricating rare-earth-free permanent magnets.
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