Barium hexaferrite monodispersed nanoparticles prepared by the ceramic method

Barium hexaferrite particles between 1 mum and 100 nm in diameter have been prepared by solid state reaction from different iron oxide precursors. The characteristics of the iron oxide precursor in terms of particle size and its distribution seem to be essential to allow us to prepare the hexaferrite at a significantly reduced temperature as well as to obtain particles with reduced size. Thus, when a goethite sample consisting of uniform particles of 200 nm length is used as iron oxide precursor, pure and uniform hexaferrite particles of around 100 nm diameter are obtained by heating up to 675 degreesC for 1 h the mixture of iron oxide and barium carbonate. Magnetic measurements of this sample showed a saturation magnetisation of around 60 emu/g at room temperature and coercivities of around 4500 Oe, in agreement with the single magnetic domain character of the particles. (C) 2001 Elsevier Science B.V. Ail rights reserved.