We propose a new method of synthesis for the preparation of nanocrystalline BaFe12O19 powders using the ammonium nitrate melt. The X-ray diffraction patterns of the calcined samples show the formation of BaFe12O19 at temperatures as low as 850degreesC. The effects of calcination temperature and time on particle size and magnetic properties are mainly studied. The magnetic measurements and structural analysis show, in good correlation, that the particles have mostly single domains but there is a tendency towards multi-domain behavior with the increase of the calcination temperature. The powders obtained by this method have better magnetic properties than those obtained by the ceramic method with a coercivity value of 4.1 kOe. (C) 2004 Elsevier B.V. All rights reserved.