BiFeO3 BF has been paid much attention recently due to its multiferroic properties. BF is ferroelectric at room temperature and ferroelectric transition temperature TC was reported to be 1103 K. Remanent polarization is very small about 3.5 C/cm2 and very large leakage currents make it difficult to measure ferroelectric properties it is antiferromagnetic TN=643 K so that it may have multiferroic properties at room temperature. Very high polarization 60 C/cm2 was, however, reported in epitaxial thin film1 and high polarization is also expected by theoretical first principle calculation.2 Large polarization and much reduced leakage current were reported in
doped BF systems later even in polycrystalline thin films.3–5 In bulk ceramics, however, the reported polarization values are not so much high as those in thin films.6–10 Then there is room for doubt that BF has so high polarization. Eerenstein et al.11 proposed a suspicion that the reported polarization could be an experimental artifact. It is necessary to solve thiscontroversy for the application of BF to real devices