To dope or not to dope: Electronic structure of Ba-site and Fe-site substituted single-crystalline BaFe2As2
The substitutional dependence of (Ba,K)(Fe,TM)2As2 (TM = Mn, Co, Ni, and Cu) is investigated with single-crystal x-ray diffraction and with near-edge x-ray absorption fine structure at the TM and Fe L2,3 edges. The present study shows that only for Ba/K replacement charge carriers are directly doped to Fe 3d states. In the case of Fe/Co substitution the additional electrons contribute to the ensemble of all 3d electrons and seem to screen the impurity whereas for Fe/Mn, Fe/Ni, and Fe/Cu replacement the data indicate that TM 4s/4p-derived impurity states become important for the electronic structure of Fe-site substituted BaFe2As2.