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Ti 3d electronic structure of Ti2O3 has been investigated by means of soft X-ray photoemission spectroscopy (SXES) in the Ti 2p–3d absorption region. In the SXES spectra, the Raman peaks due to the a 1 g – e g π and a 1 g – e g σ excitations are observed at 1.3 and 3.3 eV below the incident photon energy, respectively. The intensity of the a 1 g – e g σ peak in the SXES spectrum measured between the 2p3/2–3d and 2p1/2–3d absorption peaks depends on the polarization of the incident photon E; the peak observed clearly in case of E parallel to the c-axis, almost disappears in case of E perpendicular to the c-axis.

We measured temperature dependence of elastic modulus for the high-quality single crystals of Y 1-x Ca x TiO 3 (x = 0,0.1 and 0.2) using an ultrasonic technique. A step like elastic anomaly due to the volume magnetostriction induced by a ferromagnetic transition was observed in longitudinal C 11 and C 33 for x = 0 and 0.1, although no anomaly was observed for x = 0.2. With increasing x, the magnitude of anomaly decreases, reflecting that the amplitude of the antiferromagnetic orbital order parameter, where the orbital ordering is the origin of the ferromagnetism of YTiO 3 , is reduced with increasing Ca concentration.

We measured various elastic moduli of single-crystalline Y 1 - x Ca x TiO 3 ( x = 0 , and 0.2) as a function of temperature by means of an ultrasonic technique. Remarkable elastic softening has been found in transverse C 44 for the sample with x = 0 around 60 K, indicating structural symmetry lowering corresponding to the e yz strain. In contrast, the sample with x = 0.2 shows large softening in C 55 in response to e zx around 130 K. These results reveal that Y 1 - x Ca x TiO 3 ( x = 0 , and 0.2) undergo a structural transition and the crystal symmetry of the low temperature phase is changed by Ca-doping.