Record-High Performance 2:17-type SmCo Magnets via Fe-Driven HRE Segregation

Area of Science:

• Materials Science
• Condensed Matter Physics
• Magnetism

Background:

• High-performance samarium cobalt (SmCo) magnets are crucial for precision instruments operating across wide temperature ranges.
• A persistent challenge is the trade-off between high magnetic energy product ((BH)max) and low remanence temperature coefficient (|α|), limiting device performance.
• Conventional heavy rare-earth (HRE) substitution improves temperature stability but often reduces (BH)max.

Purpose of the Study:

• To overcome the inherent trade-off between (BH)max and |α| in SmCo magnets.
• To develop a novel compositional design strategy for high-temperature-stable SmCo magnets.
• To enable SmCo magnets for demanding applications in aerospace precision instruments.

Main Methods:

• Utilized first-principles calculations to understand the thermodynamic driving forces for HRE segregation.
• Employed molecular field simulations to quantify the effect of HRE enrichment on temperature compensation.
• Synthesized and characterized a series of SmCo magnets (Sm0.4Gd0.6(CobalFexCuyZr0.025)7.2) with varying Fe concentrations (x = 0.20-0.24).

Main Results:

• Demonstrated that increasing Fe concentration promotes HRE segregation into the 2:17R phase.
• Showcased that HRE enrichment in the 2:17R phase enhances temperature compensation, mitigating the (BH)max vs |α| trade-off.
• Achieved a record-high (BH)max of 18.8 MGOe and a low |α| of -0.012%/°C (20°C-300°C) in SmCo magnets with moderate Fe enrichment (x=0.22).

Conclusions:

• Established a synergistic Fe-HRE compositional design strategy to break the (BH)max-|α| trade-off in SmCo magnets.
• Developed a unified design framework integrating magnetic moment engineering and thermodynamic element distribution.
• Paved a viable path for next-generation high-temperature-stable SmCo magnets for aerospace and other precision instrument applications.