Tm-Substituted 2:17-type magnets: balancing room-temperature magnetic properties and temperature stability

Area of Science:

• Materials Science
• Condensed Matter Physics
• Magnetism

Background:

• Permanent magnets require high thermal stability and room-temperature performance, which traditional magnets struggle to achieve simultaneously.
• Samarium-cobalt (SmCo) magnets are crucial for high-performance applications but face limitations in thermal stability.

Purpose of the Study:

• To develop a novel Thulium-substituted (Sm,Tm)2Co17 magnet with enhanced thermal stability and maintained high room-temperature magnetic properties.
• To investigate the effects of Thulium substitution on the phase stability, microstructure, and magnetic performance of SmCo magnets.

Main Methods:

• First-principles calculations to understand the role of Thulium in phase stabilization.
• Microstructural analysis using advanced techniques to examine phase evolution and precipitate formation.
• High-temperature processing optimization to refine microstructure and enhance magnetic properties.

Main Results:

• The Tm-substituted (Sm,Tm)2Co17 magnet achieved a low remanence temperature coefficient (α20–150°C = -0.008%/°C) and high room-temperature properties (BHmax = 19.26 MGOe, Br = 9.25 kG, Hcj = 9.94 kOe).
• Thulium substitution was found to stabilize the desired 2:17H phase but initially weakened coercivity due to altered cellular structure and reduced pinning.
• Optimized high-temperature processing significantly increased coercivity to 25.03 kOe (152% enhancement) by refining the microstructure and improving copper partitioning.

Conclusions:

• The developed (Sm,Tm)2Co17 magnet offers a unique combination of excellent thermal stability and high magnetic performance.
• This study presents a viable design paradigm for advanced, temperature-compensated permanent magnets.
• The findings are highly relevant for demanding applications in aerospace, military, and precision instrumentation.