Magnetic and structural properties of L10 FePt/MnFe2O4 nanocomposites

• Monodispersed 4.1 nm FePt nanoparticles were successfully synthesized by the chemical polyol process.
• High temperature (usually higher than 550 °C) annealing is necessary to obtain L10 ordered structure.
• Annealing causes the surfactant start to decompose and sintering of particles take place.
• MnFe2O4 shell were used as the shell around of each FePt core particles to prevent them from sintering.
• MnFe2O4 shell with magnetic behavior exposed exchange-coupled interaction with the magnetic core particles.

Monodispersed 4.1 nm FePt nanoparticles were successfully synthesized by the chemical polyol process with co-reduction of iron acetylacetonate, Fe(acac)3 and platinum acetylacetonate, Pt(acac)2. High temperature (usually higher than 550 °C) annealing is necessary to obtain L10 ordered structure. The agglomeration of particles takes place during post-annealing process. In the present work, we prevent sintering of FePt nanoparticles during the annealing process at temperatures of 750 and 850 °C by using nanocomposite structure. In this case, MnFe2O4 nanoparticles were used successfully to preserve particles from sintering. The results show a decrease in coercivity by adding MnFe2O4 in nanocomposite. This might be due to the effective exchange coupling happens between FePt and MnFe2O4 parts. Furthermore, the well isolated L10 FePt nanoparticles with coercivity of 4300 Oe are prepared and magnetic properties of L10–FePt–MnFe2O4 nanocomposite are studied.

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