Phase stability, oxygen nonstoichiometry and magnetic properties of BiFeO3-δ -: art. no. 252510

The phase stability of polycrystalline BiFeO3-delta (BFO) was measured using coulometric titration in the technologically important temperature range for growth of epitaxial thin films, 680 degrees C-800 degrees C. BFO exhibits only a very narrow oxygen nonstoichiometry, i.e., delta < 0.01. For the most nonstoichiometric sample obtainable at 800 degrees C (containing a maximum Fe2+ fraction of 2 mol %) the saturation magnetization was 3.1x10(-4)mu(B)/Fe, a factor of around 2 higher than a nominally fully oxygenated sample. Hence, the contribution of Fe2+ to the ferromagnetism is small. The decomposition products of BFO below the oxygen phase stability line are Bi25FeO40-x and gamma-Fe2O3. (c) 2005 American Institute of Physics.