This study reports on the structural and magnetic characterizations of free-standing bismuth ferrite, BiFeO 3, nanoparticles synthesized in polyol medium. Fine tuning of the ferrite magnetic properties was achieved by adding an excess bismuth species or doping with cobalt ions, coupled with thermal annealing. Crystalline Bi 1-yCo yFeO 3 powders (where 'y' ranges from 0.00 to 0.10) were produced after annealing the precursors for one hour at 70O 0C The average crystallite size was calculated to be approximately 22 nm. We found that the synthesis under stoichiometric excess of Bi species (up to 10 at.%) promoted a more complete crystallization of the material, i.e., no precursor phases remained. Furthermore, both the saturation magnetization and the coercivity of the synthesized powders were strongly influenced by the concentration of Co. They increased from 0.13 emu/g and 19 Oe to 3.5 emu/g and 1183 Oe for pure BiFeO 3 and 10 at.% Co-doped BiFeO 3, respectively. © 2011 Materials Research Society.