Production and Characterization of Nanostructured Powders of NdFeB and FeAl by Mechanical Alloying.

The objective of this work is to evaluate the applicability of exchange coupling between nanoparticles of NdFeB (hard magnetic material) and FeAl (soft magnetic material), as permanent magnets produced by surfactant-assisted mechanical alloying. The obtained powders were then mixed with 85% of the NdFeB system and 15% of the FeAl system and subsequently sintered at 300 °C, 400 °C and 500 °C for one hour. The results obtained by Mössbauer spectrometry (MS) show a ferromagnetic behavior with six magnetic sites represented by sextets (16k1, 16k2, 8j1, 8j2, 4c and 4e), characteristic of the NdFeB system. X-ray diffraction (XRD) results show a tetragonal and BCC structure for the NdFeB and FeAl systems, respectively. The results obtained by vibrating sample magnetometry (VSM), for mixtures of the NdFeB and FeAl sy stems sintered at 300 °C, 400 °C and 500 °C, allow for the conclusion that the coercive field (Hc) decreases drastically with temperature and the percentage of soft phase at values of Hc = 132 Oe compared to the coercive field values reported for NdFeB Hc = 6883 Oe, respectively. Images obtained by transmission electron microscopy (TEM), for the FeAl system, show a tendency for the nanoparticles to agglomerate.