Preparation of ultrafine FePt nanoparticles by chemical reduction in PAMAM-OH template

Using dendrimer templates, FePt nanoparticles with narrow size-distribution were prepared by a simple chemical reduction method at room temperature. In this approach, PAMAM-OH dendrimers act as templates in which metal ions are coordinated in, and NaBH4 acts as reductant. The FePt nanoparticles were synthesized in aqueous solution. The as-made FePt nanoparticles are spherical with an average size of ∼3 nm and have the chemically disordered face-center-cubic (fcc) structure. The FePt nanoparticles can be transformed to the face-center-tetragonal (fct) phase after annealing at 700 °C for 1 h. The as-prepared fcc FePt nanoparticles are found to be superparamagnetic at room temperature. After annealing in a reducing atmosphere, the FePt nanoparticles transform to ferromagnetic and show high covercivity. The structural and magnetic properties of the as-made and annealed FePt nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and alternating gradient magnetometry (AGM).