Formation of FePt nanoparticles having high coercivity

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Iron-platinum (FePt) nanoparticles are crucial for high-density magnetic storage media.
• Achieving the face-centered tetragonal (fct) phase with high coercivity at low temperatures is a key challenge.

Purpose of the Study:

• To synthesize surface-capped face-centered cubic (fcc) FePt nanoparticles using a novel precursor.
• To investigate the phase transition of these nanoparticles to the ferromagnetic fct phase.
• To characterize the magnetic properties, specifically coercivity, of the resulting FePt nanocrystals.

Main Methods:

• Ultrasonication of a heteropolynuclear Pt3Fe3(CO)15 cluster complex in toluene with oleic acid and oleylamine.
• Self-assembly of synthesized nanoparticles onto oxidized silicon wafers.
• Annealing the self-assembled arrays at 775°C to induce the fcc-to-fct phase transition.
• Characterization of nanoparticle size, phase, and magnetic coercivity using appropriate techniques.

Main Results:

• Surface-capped fcc FePt nanoparticles (average diameter ~2 nm) were successfully synthesized.
• A fcc-to-fct phase transition occurred at 775°C, forming well-dispersed ferromagnetic FePt nanocrystals (~5.8 nm).
• The annealed FePt nanoparticles exhibited a high room-temperature coercivity of approximately 22.3 kOe.

Conclusions:

• The use of a heteropolynuclear complex as a single-source precursor and ultrasonication facilitates the formation of FePt nanoparticles with high coercivity.
• The observed high coercivity suggests potential for advanced magnetic storage applications.
• Further experiments are ongoing to determine the critical conditions for achieving high coercivity in ferromagnetic nanoparticles.