I don't understand while doing XPS I m getting Fe2+ peak for BiFeO3 and Fe2o3 samples. Fe is in +3 states in BiFeO3 and Fe2O3. So, why I m getting Fe2+ in that sample?
We really need to see the data. If you have Fe2O3 you will have a satellite peak at ~ 719 eV in the Fe(2p) spectrum in addition to the Fe(2p3/2) peak at ~ 711 eV.
Alternatively, from the way you've worded the questions it sounds like you have only Fe2+? If that is the case then I would suggest your data is incorrectly calibrated.