Theory of Ordered State of Multiparty Freedoms of Atoms and X-Ray Spectroscopy and Scattering

(1)钙钛矿型过渡金属氧化物的轨道态和X射线吸收线性二色性我们在微扰计算的基础上研究了钒钙钛矿型氧化物LaVO_3和YVO_3中V离子的三维自旋-轨道相互作用对V-V电子转移的影响，结果表明，V的轨道磁矩对总磁矩有很大的贡献。对于YTi03，除了c方向的铁磁分量外，在ab平面上还观察到了多种反铁磁调制，我们提出了自旋和轨道矩之间的非共线性可以解释不止一种额外的调制。我们进一步指出，在许多具有反英雄轨道有序的钙钛矿中都可以观察到X射线对线性二向色性信号的吸收，这与反铁磁体中没有X射线吸收磁二向色性信号形成了鲜明的对比。(2)V203V203的反铁磁有序理论表明，随着温度的降低，金属-绝缘体转变。在低温反铁磁相中，晶体对称性由高温相的刚玉结构转变为单斜晶系，表现出反常的磁结构，反映了低对称性的晶体结构。通过扩展V离子对模型，计算了V离子对之间的交换相互作用，表明交换相互作用的符号对晶格扭曲很敏感，并解释了磁有序现象，而不假定迄今提出的轨道有序模型。

(1) Orbital States in Perovskite-Type Transition-Metal Oxides and X-Ray Absorption Linear DichroismWe investigated the effect of 3d spin-orbit interaction in V ion in vanadium perovskite-type oxides including LaVO3 and YVO3 on the basis of the perturbation calculation with respect to the V-V Electron transfer and showed that the orbital magnetic moment of V can considerably contribute to the total moment. For YTi03, where in addition the ferromagnetic component in the c-direction, more-than-one kinds of antiferromagnetic modulations are observed in the ab plane, we proposed that a non-collinearity between the spin and orbital moments can explain the more-than-one additional modulations. We furthermore pointed out that the x-ray absorption on linear dichroism signal is to be observed in many perovskites with antihero-orbital orderings, which is in sharp contrast to the absence of x-ray absorption magnetic circular dichroism signal in antiferromagnets.(2) Theory of Antiferromagnetic Ordering in V203V203 is know to exhibit a metal-insulator transition with decreasing the temperature. In the low temperature antiferromagnetic phase, the crystal symmetry changes from the corundum structure in the high temperature phase to the monoclinic one and it shows anomalous magnetic structure reflecting the low symmetry crystal structure. We calculated, by extending the V-ion pair model, the exchange interaction between V-ion pairs and showed that the sign of the exchange interaction is sensitive to the lattice distortion and explain the magnetic ordering without assuming the so far proposed orbital-ordering model.