Preparation and characterization of nano-scale Fe₂P-based particles by surfactant-assisted high-energy ball milling

Magnetocaloric nanoparticles based on the Fe₂P system have been prepared by ball milling in the presence of the organic solvent heptane and the surfactant oleic acid. The surfactant is used to prevent the re-welding of crushed particles during the ball milling and to enhance the dispersion of nanoparticles in the solvent [1]. A size selection process using centrifugation and ultrasonic vibration was employed after ball milling to obtain nanoparticles with a narrow size distribution. The XRD peak intensity decreases while the peaks broaden in the presence of surfactant and solvent, indicating a decrease in particle size and an increase in the degree of amorphization. The magnetization of the nanoparticles obtained by surfactant-assisted high-energy ball milling decreased compared to the bulk. This can be attributed to a larger contribution of the surface states due to the size reduction, amorphization and contamination such as residual surfactant. The effect of milling parameters on Fe2P-based compounds as nano-scale particles as well as their dynamic response by nanosizing will be discussed in detail.