Bulk SmCo5/a-Fe nanocomposite permanent magnets fabricated by mould-free Joule-heating compaction

Bulk SmCo5/a-Fe nanocomposite magnets have been prepared using a Joule-heating compaction technique. Nearly fully dense bulk magnets are obtained by compacting the milled powders under a pressure of 2 GPa at temperatures above 400 C. Structural analysis shows that the grain size of both the SmCo5 and the a-Fe phases is in the range of 10 to 15 nm when the compaction temperature is lower than 500 C, which ensures effective interphase exchange coupling. A further increase in compaction temperature leads to significant grain growth and deterioration of magnetic properties. A maximum energy product of about 18.5 MGOe was obtained in the bulk SmCo5/a-Fe nanocomposite magnets, which is 90% higher than that of the single-phase counterpart prepared under the same conditions. VC 2011 American Institute of Physics. [doi:10.1063/1.3563098]