Soft X-ray Absorption Spectroscopy Study of Multiferroic Bi-substituted   Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3)
  The electronic structures of multiferroic oxides of Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3) (0 < x < 0.12) have been investigated by employing photoemission spectroscopy and soft x-ray absorption spectroscopy (XAS). The measured Fe and Ti 2p XAS spectra show that Ti ions are in the Ti4+ states for all x and that Fe ions are Fe2+-Fe3+ mixed-valent for x > 0. The valence states of Fe ions are found to be nearly trivalent for x=0, and decreases with increasing x from being nearly trivalent (v(Fe)~ 3) for x=0 to v(Fe)~ 2.6 for x=0.12. The valence states of both Ti and Ba ions do not change for all x < 0.12. Based on the obtained valence states of Fe ions, the electronic and magnetic properties of Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3) are explored. 
Hyun Woo Kim, D. H. Kim, Eunsook Lee, Seungho Seong, Deok Hyeon Kim,   B. W. Lee, Y. Ko, J.-Y. Kim, J.-S. Kang
cond-mat.mtrl-sci