Ferromagnetic FePt/Au Core/Shell Nanoparticles Prepared by Solvothermal Annealing

We report a novel multistep process for the preparation of monodisperse ferromagnetic FePt/Au core/shell nanoparticles. Disordered face-centered cubic (fcc) FePt nanoparticles were first synthesized by a polyol method. FePt/Au core/shell superparamagnetic nanoparticles were then produced via a reductive decomposition of gold acetate in the presence of the FePt seed nanoparticles. The FePt/Au core/shell nanoparticles were annealed in benzyl ether using an autoclave reactor at a temperature of 470°C for 3 h at 7 MPa (1000 psi). Morphological, structural, and magnetic characterization of the FePt/Au core/shell nanoparticles was performed before and after the solvothermal annealing. The annealed monodisperse FePt/Au nanoparticles transformed from a disordered superparamagnetic fcc to a partially ordered ferromagnetic L1₀ phase with a coercivity up to 2.8 kOe at room temperature.