Bulk FePt/Fe_3Pt nanocomposite magnets prepared by spark plasma sintering

摘要

FePt/Fe_3Pt bulk nanocomposite magnets have been prepared by the spark plasma sintering of chemically synthesized FePt and Fe_3O_4 nanoparticles under 100 MPa at 400-600℃. It was found that the phase transition of the FePt compound from the face centered cubic to the L1_0 started at 500℃ and was almost completed at 600℃ 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℃. Pressure rather than temperature was more effective in enhancing intergrain exchange coupling compared to temperature.