Photon Factory Activity Report 2004 #22 Part B (2005)
Electronic Structure of Condensed Matter

7C/2004G193

Resonant Inelastic Light Scattering of Ti Compounds
1*1

23Yasuhisa TEZUKA , Toshiyuki SASAKI , Toshiaki IWAZUMI , Hitoshi OSAWA ,4
Yasuhito ISOZUMI1
Hirosaki University, 3 Bunkyo-cho, Hirosaki 036-8561, Japan
2
KEK-PF, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
3I SSP, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8581, Japan
4
Kyoto University, Konoe-cho, Yoshida, Sakyo-ku, Kyoto 606-8501, JapanIntroduction
Early TM compounds including Ti compounds haveattracted the interest of researchers because of their strong
hybridization energies [1]. Many body effects are observed inhigh energy spectra of these compounds [2-4]. TiO2 has beenstudied for a long time, because of its important applications
such as photocatalyst and its interesting solid-state properties.
BaTiO3 is one of typical ferroelectrics and it was suggested thathybridization affects its ferroelectricity [5]. Ti2O3 is known tobe the typical MH type semiconductors that have narrow bandgap (Egap < 0.1 eV) in the insulator phase, which undergoes
metal-insulator transition at about 200 °C Nominally, Ti2O3 has
one 3d electron, while the others have no 3d electron.
Resonant inelastic X-ray light scattering (RIXS) of Ticompounds were observed in this experiment.

Experimental
The experiments were performed at the beamline BL-7C in
Photon Factory, KEK. X-ray emitted from the sample wasanalyzed using cylindrically bent crystals Ge 100. X-rayemission spectrum (XES) was recorded by the position-sensitive
proportional counter (PSPC). Energy resolution was estimatedto be about 2.0 eV in the measurements energy range.
Powdered samples were measured in this experiment. Eachcrystal includes the TiO6 octahedron. In Oh symmetry, the 3dstate is split into a lower t2g and a higher eg state by crystal field.
BaTiO3 and TiO2 have lower symmetry of C4v and D4h,respectively. In the case of Ti2O3, the t2g state is further split into
the a1g and eg states, since it has a corundum structure with atrigonal Bravais lattice (C3v).

Fig.1 Ti-K XAS spectra of Ti compounds. Vertical bars
indicate excitation energy of RIXS.

Results and Discussions
Figure 1 shows Ti-K XAS spectra of Ti-compounds. The
main structures above 4975 eV originate from Ti 1s → 4p dipoletransition, while pre-edge structures around 4970 eV originate
from Ti 1s → 3d quadrupole transitions. These spectra showquite different spectra. Especially, Ti2O3 that have finite delectron shows rather broad spectrum than those of the others. In
this experiment, RIXS spectra of these materials were observedin the energy range of the pre-edge region.
Figure 2 shows RIXS spectra of Ti-compounds. Thesespectra were excited at about 4985 eV that is the main peakenergy of Ti-K XAS. An inelastic peak originated from chargetransfer (CT) excitation is observed in each spectrum. Nominald-electron in Ti2O3 does not affect these spectra. This result is incontrast to the Ti 2p resonant Raman scattering study of Ti2O3,
in which the strong d-d excitations are observed rather than theCT excitation [6].

References[1] K. Okada et al., J. Electron Spectrosc. Relat. Phenom.,
62, 131 (1993).
[2] T. Uozumi, et al., J. Phys. Soc. Jpn., 65, 1150 (1996).

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Fig. 2 RIXS spectra of Ti compounds. The verticaldotted line at 0 eV indicates elastic peak and anotherindicates the Raman peaks of CT excitation. Higher[3] Y. Tezuka et al., J. Phys. Soc. Jpn. 65, 312 (1996).
[4] Y. Harada et al., Phys. Rev. B 61, 12854 (2000).
[5] R.E. Cohen, Nature, 358, 136 (1992).
[6] Y. Tezuka, PF Activity Report (2005).
* tezuka@si.hirosaki-u.ac.jp