Direct Observation of Orbital Ordering in Light Transition Metal Oxides by Soft-X Ray Core Absorption Spectroscopy with Linearly Polarized Light

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We have developed the experimental system to observe a linear dichroism in core absorption spectra using soft X-ray synchrotron radiation at Hiroshima Synchrotron Radiation Center (HSRC) of Hiroshima University. Using this system, we study orbital ordering, which possibly exists in several 3d transition metal oxides involving Ti and V atoms. These transition metal oxides are fabricated in our group. Our research goal is to find if the orbital ordering exists in these transition metal oxides and also to relate the spin ordering with the orbital ordering.During the first fiscal year (H13), we have developed the observation system, which was attached to the beam-line of HiSOR, the strage ring at HSRC. We also attached the cryostat with the heater to the sample manipulator, which enabled us to change the sample temperature from 10K to 300K. In the first fiscal year, we newly bought a low energy electron diffraction (LEED) system for the check of the sample surface cleanliness. We finished the adjustment of the beamline at HiSOR by the end of the year (H13). As a result, we could use the light beam in the photon energy range of 400-1000eV with the photn flux of 10^8-10^9 photons/sec. At the second fiscal year, we actually performed the experiment on single crystalline VTiO3, which has been fabricated in our research group. We could observe the difference between the absorption coefficients with the light polarization vector parallel to a and b axes. We are now analyzing data and going to clarify the relationship between the orbital ordering and the physical properties.