Soft magnetic nanoparticles of BaFe12O19fabricated under mild conditions

Nanoparticles of barium hexaferrite, with an average size of 12 nm, were prepared by a hydrothermal route at relatively low temperatures (140–180 °C). The effects of reaction temperature and time on the particle size and magnetic properties were discussed. The nanoparticles show a soft magnetic feature with a saturation magnetization of 1.1 emu g−1 and coercivity of 221.0 Oe, rather than the hard magnetic characteristic that the corresponding bulk material exhibits. Annealing treatment in air at 800 °C led to an order-of-magnitude increase of the saturation magnetization (67.3 emu g−1) and coercive force (4511 Oe). It is suggested that the oxygen vacancies should be responsible for the soft magnetic characteristic that appeared for the as-prepared barium hexaferrite nanoparticles.