Phase Transformation in Silica-Coated FePt Nanoparticles

Chemically synthesized FePt nanoparticles (NPs), with an average size of 5.8 nm, were coated with silica (SiO
₂
) shells. The thickness of the silica shell could be controlled between 7.5-25 nm. A modified heating profile has been adopted with which silica shell cracking at high temperatures (1000degC) could be prevented. Even with prolonged heating for 24 h at 800degC, no sintering of the particles is observed. Low temperature (7 K) and room temperature magnetization scans show low coercivity values which are possibly due to a compositional distribution among the individual NPs.