Processing and characterization of Nd_2Fe_(14)B microparticles prepared by surfactant-assisted ball milling

摘要

The synthesis of hard magnetic nanoparticles based on the Nd2Fe14B system has been studied by means of surfactant-assisted ball milling technique. The XRD results show that, in the range of milling time employed (5, 10 and 20 h), a majority of Nd2Fe14B phase was detected in the nanoparticles, indicating that no oxidation took place during milling. Mossbauer spectra were fitted with seven sextets, which correspond to the six ferromagnetic sites of the hard phase and alpha-Fe, and a doublet corresponding to the paramagnetic Nd1.1Fe4B4 phase. It has been observed that the nanoparticles prepared by milling showed elongated rod shapes and ferromagnetic behavior at room temperature with coercivity up to 6.4 kOe obtained after milling at 5 h, decreasing with longer milling times.