the search of the orbital ordering of the magnetic moment by using x-ray magnetic scattering

我们研究了强关联电子系统中的“高温超导“和/或“巨磁阻”现象。为了探索这一重要问题，我们首先利用同步辐射X射线散射新技术研究了一种新的“有序”自由度：首先，我们仔细研究了磁性金属元素Mn阳离子在K边能量处发生的轨道有序共振X射线散射的机制。发现了4p与处于轨道有序态的3d轨道之间的库仑内相互作用提高4p简并度的机制。然后，它会产生增强或共振。然后利用同步辐射X射线散射技术，对LaMnO_3中由Jahn-Teller效应引起的轨道有序进行了深入的研究，并将其推广到CMR材料中掺杂锰氧化物中金属绝缘体的相变研究。我们发现相变是由轨道的有序-无序转变触发的。第三，我们将近两年来所研究的项目扩展为一个新的项目，目标是研究轨道涨落的标准探针。

We have studied the "high temperature superconductivity " and /or "colossal magnetoresistance (CMR)" as the key phenomena in the strongly correlated electron systems. In order to explore this important issue, we initiated to investigate a novel degree of freedom of "order" by using new technique of the synchrotron x-ray scattering besides neutron scattering.First we studied carefully the mechanism of the resonant x-ray scattering of the orbital order occurred at the energy of K edge of the magnetic metal element, actually Mn cations. Then we found the mechanism that the intra Coulomb interaction between 4p and 3d orbital which is in the orbital ordered state lifts the 4p degeneracy. Then it gives rise an enhancement or resonance. Then we deeply studied the orbital order in LaMnO_3 originated by the Jahn Teller effect by using this newly established technique of the synchrotron x-ray scattering.Second, we also extend this technique to study the phase transition of metal insulator in the doped manganites as recognized the CMR materials. We found that the phase transition is triggered by the orbital order-disorder transition.Third, we extend this project studied during the recent two years granted to a new project aiming the standard probe of studying the orbital fluctuations.