Bulk FePt∕Fe3Pt nanocomposite magnets prepared by spark plasma sintering

Fe Pt ∕ Fe 3 Pt bulk nanocomposite magnets have been prepared by the spark plasma sintering of chemically synthesized FePt and Fe3O4 nanoparticles under 100MPa at 400–600°C. It was found that the phase transition of the FePt compound from the face centered cubic to the L10 started at 500°C and was almost completed at 600°C during the sintering. The activated atomic diffusion during the phase transition led to a significant increase in density. The density about 70% of the theoretical value has been obtained. Grain size of the sintered samples remains nanoscale even after a postannealing at 700°C. Pressure rather than temperature was more effective in enhancing intergrain exchange coupling compared to temperature.