Study of Fe-rich FePt nanoparticles synthesized by a single step reverse micelle route

Fe-rich FePt nanoparticles with an average size of 5 nm were prepared using a reverse micelle route. As synthesized FePt powders were disordered face centered cubic in structure. DSC thermogram displays phase transformation at 575 °C, based on which heat treatments were carried in the temperature range of 500–600 °C. XRD patterns show that the degree of ordering increased with the increase in heat treatment temperature. An utmost coercivity of 3.2 kOe was observed for 600 °C heat-treated sample. The M–H loops were asymmetric in nature suggesting the presence of a second phase, Fe-oxide (Fe3O4) that is also observed from the XRD patterns. Mössbauer spectra reveals that on heat treatment the super-paramagnetic phase transforms into an ordered face centered tetragonal phase. The presence of 23% super-paramagnetic phase even after heat-treating at 600 °C reveals that the phase transformation is incomplete.