Probing the Ba 5d states in BaTiO and BaSO; A Resonant X-ray emission study at the Ba-L edge

Yoshii, Kenji  ; Jarrige, I.; Suzuki, Chikashi ; Matsumura, Daiju   ; Nishihata, Yasuo; Yoneda, Yasuhiro   ; Fukuda, Tatsuo  ; Tamura, Kazuhisa   ; Ito, Yoshiaki*; Mukoyama, Takeshi*; Tochio, Tatsunori*; Shinotsuka, Hiroshi*; Fukushima, Sei*

We have directly probed the Ba 5d states in the ferroelectric barium titanate BaTiO using resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L edge. The results are compared with those of the non-ferroelectric BaSO. While the RXES spectra point to a localized character for the Ba 5d states in both compounds, the main peak of the PFY-XAS spectrum, corresponding to the dipolar transitions from 2p to 5d, is found to be significantly broader for BaTiO than for BaSO. On the basis of band structure calculations, this broadening is ascribed to strong hybridization between the unoccupied Ba 5d and O 2p states in the ferroelectric. This suggests that the hybridization between the conduction states of the Ba and O ions, and not only Ti and O, plays a central role in determining the electronic structure of BaTiO.