Thermal stability of MnBi magnetic materials

Area of Science:

• Materials Science
• Solid State Physics
• Magnetism

Background:

• Manganese-Bismuth (MnBi) is a promising rare-earth-free permanent magnet material.
• Its unique temperature-dependent coercivity is ideal for exchange coupling nanocomposite magnets.
• Challenges include the peritectic reaction and Mn oxidation, forming detrimental MnO.

Purpose of the Study:

• To develop scalable production methods for high-purity MnBi permanent magnets.
• To characterize the magnetic properties and thermal stability of the synthesized MnBi.
• To evaluate its potential as a viable alternative to rare-earth magnets.

Main Methods:

• Developing a process for routine, large-scale production of high-purity (>90%) MnBi.
• Measuring magnetic properties, including saturation magnetization and maximum energy product ((BH)max).
• Assessing thermal stability in air up to 473 K.

Main Results:

• Successfully produced high-purity MnBi powder in large quantities.
• Achieved a saturation magnetization of 74.6 emu/g at room temperature.
• Obtained a maximum energy product ((BH)max) of 11.9 MGOe for aligned powder and 7.8 MGOe for sintered bulk magnets.
• Confirmed thermal stability in air up to 473 K.

Conclusions:

• The developed method enables routine production of high-purity MnBi.
• The material exhibits excellent magnetic properties suitable for permanent magnets.
• MnBi demonstrates good thermal stability, making it a strong candidate for rare-earth-free magnet applications.