Rapid thermal annealing of FePt nanoparticles

We report a systematic study on rapid thermal annealing (RTA) of FePt nanoparticles. FePt particles with an average size of 8nm were synthesized by a chemical solution method, and then annealed using RTA and conventional furnace annealing (FA). It was observed that FePt nanoparticles can be transformed from disordered A1 phase to ordered L10 phase at 650°C for 10s using RTA, which is much shorter than the time needed for FA. The transmission electron microscopy and x-ray diffraction studies have revealed that the particle agglomeration and grain growth in the RTA treated samples are much less than in the FA treated samples. A linear correlation between the coercivity and the square root of the treatment time t was observed in the RTA treated samples, which implies that the phase transition is related to atomic diffusion of Fe atoms from Fe-rich shells into the Pt-rich cores.