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

我们在广岛大学的广岛同步辐射中心（HSRC）开发了利用软X射线同步辐射观测堆芯吸收光谱线性二向色性的实验系统。利用这个系统，我们研究了几种包含Ti和V原子的3d过渡金属氧化物中可能存在的轨道有序。这些过渡金属氧化物是在我们小组中制备的。我们的研究目标是发现这些过渡金属氧化物中是否存在轨道有序，并将自旋有序与轨道有序联系起来。在第一个财政年度（H13），我们已经开发了观测系统，该系统连接到HSRC的希索束线，即Strage环。我们还将带有加热器的低温恒温器连接到样品操纵器上，这使我们能够将样品温度从10 K改变到300 K。在第一个财政年度，我们新购买了一台低能电子衍射（LEED）系统，用于检查样品表面的清洁度。我们在年底（H13）完成了希索光束线的调整。因此，我们可以使用光子能量范围为400- 1000 eV的光束，光通量为10^8-10^9光子/秒。在第二个财政年度，我们实际上进行了实验的单晶VTiO 3，这已经在我们的研究小组制造。我们可以观察到光偏振矢量平行于a轴和B轴时吸收系数之间的差异。我们现在正在分析数据，并将澄清轨道排序和物理性质之间的关系。

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.