Dispersible SmCo₅ nanoparticles with huge coercivity.

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Chemistry

Background:

• Sintering of samarium cobalt (SmCo5) particles during calciothermic reduction hinders the synthesis of dispersed magnetic materials.
• Achieving high coercivity in permanent magnets is crucial for advanced technological applications.

Purpose of the Study:

• To develop a new synthesis strategy for producing dispersible SmCo5 nanoparticles.
• To investigate the coercivity mechanism and achieve record-high coercivity in SmCo5 nanoparticles.

Main Methods:

• Co-precipitation of amorphous Sm(OH)3 and nanoscale Co(OH)2 and Ca(OH)2 crystallites to form a precursor.
• Calciothermic reduction at 860 °C, utilizing a CaO isolation shell to prevent sintering.
• Dissolution of CaO, followed by particle dispersion and orientation in an external magnetic field.

Main Results:

• Successfully synthesized dispersible SmCo5 nanoparticles with a CaO isolation shell preventing sintering.
• Achieved high magnetization (90 Am2 kg-1) and remanence ratio (0.96).
• Obtained record-high coercivity of 6.6-7.2 T at room temperature, attributed to nucleation and growth in a thin surface layer.

Conclusions:

• The novel co-precipitation and calciothermic reduction method effectively prevents sintering and yields high-performance SmCo5 nanoparticles.
• The identified coercivity mechanism in a low-anisotropy surface region offers insights for designing future permanent magnets.
• The achieved coercivity in SmCo5 nanoparticles opens prospects for advanced high-temperature magnetic composites.