Masaki Takemura

Ti 3d orbital change across metal-insulator transition in Ti2O3 : Polarization-dependent soft X-ray absorption spectroscopy at Ti 2p edge

The Ti 3 d electronic structure of Ti 2 O 3 across metal–insulator transition (MIT) has been investigated by means of polarization-dependent soft X-ray absorption spectroscopy (XAS) at the Ti 2 p edge. The XAS spectra exhibit a remarkable linear dichroism (LD) between the polarization vectors of the incident light parallel and perpendicular to the Ti ion pair along the c -axis. LD intensity is significantly reduced at 520 K in the metallic phase in comparison with that at 300 K in the insulating phase, indicating a large change in a 1 g and e g π orbital occupations. The results are qualitatively consistent with a recent theory, where the MIT is due to the change of the 3 d electronic configuration in the Ti pair along the c -axis driven by a change in the t 2 g level splitting relative to the on-site exchange interaction.

Hole-doping and Pressure Effects on the Metal–Insulator Transition in Single Crystals of Y1-xCaxTiO3 (0.37 ≤x ≤0.41)

The measurements of electrical resistivity, magnetic susceptibility, specific heat, thermopower and powder x-ray diffraction under pressure have been performed on single crystals of Y 1- x Ca x TiO...

Elastic anomaly around a ferromagnetic transition in Y1-xCaxTiO3 (x=0–0.2)

We measured temperature dependence of elastic modulus for the high-quality single crystals of Y1-xCaxTiO3Y1-xCaxTiO3 (x=0,0.1x=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 C11C11 and C33C33 for x=0x=0 and 0.1, although no anomaly was observed for x=0.2x=0.2. With increasing xx, 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 YTiO3, is reduced with increasing Ca concentration.

Elastic anomaly around a ferromagnetic transition in Y1-xCaxTiO3Y1-xCaxTiO3 (x=0x=0–0.2)

We measured temperature dependence of elastic modulus for the high-quality single crystals of Y1-xCaxTiO3Y1-xCaxTiO3 (x=0,0.1x=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 C11C11 and C33C33 for x=0x=0 and 0.1, although no anomaly was observed for x=0.2x=0.2. With increasing xx, 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 YTiO3, is reduced with increasing Ca concentration.

Elastic anomaly around a ferromagnetic transition in (–0.2)

We measured temperature dependence of elastic modulus for the high-quality single crystals of Y1-xCaxTiO3Y1-xCaxTiO3 (x=0,0.1x=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 C11C11 and C33C33 for x=0x=0 and 0.1, although no anomaly was observed for x=0.2x=0.2. With increasing xx, 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 YTiO3, is reduced with increasing Ca concentration.