Synthesis of CoPt nanoparticles by a modified polyol method: characterization and magnetic properties

Area of Science:

• Materials Science
• Nanotechnology
• Magnetism

Background:

• Cobalt-Platinum (CoPt) nanoparticles are promising for magnetic applications due to their tunable magnetic properties.
• Achieving ordered structures in CoPt nanoparticles is crucial for enhancing magnetic performance.
• Controlling nanoparticle size and phase is key to unlocking advanced magnetic functionalities.

Purpose of the Study:

• To synthesize highly uniform, small-sized CoPt nanoparticles.
• To investigate the structural transformation of CoPt nanoparticles upon thermal treatment.
• To evaluate the magnetic properties, specifically coercivity, of the resulting CoPt nanostructures.

Main Methods:

• Chemical reduction of cobalt acetate and platinum acetylacetonate using polyethyleneglycol-200 as a reducing and capping agent.
• Synthesis of CoPt nanoparticles with an average diameter of 3 nm and narrow size distribution.
• Thermal treatment to induce structural phase transformation from disordered fcc to ordered fct.
• Magnetic property measurements at room temperature and 5 K.

Main Results:

• Successfully synthesized 3 nm CoPt nanoparticles with a narrow size distribution.
• Observed a structural transition from a disordered face-centered cubic (fcc) to an ordered face-centered tetragonal (fct) phase after annealing.
• Achieved high coercivity values: 6 kOe at room temperature and 9 kOe at 5 K.
• Correlated the enhanced coercivity to the high magnetocrystalline anisotropy of the ordered tetragonal phase.

Conclusions:

• The synthesis method yields uniform CoPt nanoparticles suitable for further structural modification.
• Thermal treatment is an effective strategy to achieve the ordered fct phase in CoPt nanoparticles.
• The significant increase in coercivity demonstrates the potential of these ordered CoPt nanoparticles for high-performance magnetic applications.