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

原子多方自由有序态理论与X射线光谱学和散射

基本信息

批准号：
13640365
负责人：
JO Takeo
金额：
$ 0.83万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

(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.

(1)钙钛矿型过渡金属氧化物中的轨道态和X射线吸收线性二向色性我们在微扰计算V-V电子转移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3d自旋-轨道相互作用的影响，发现V的轨道磁矩对总磁矩有很大贡献。对于YTi 03，除了c方向的铁磁分量外，在ab平面上还观察到了不止一种反铁磁调制，我们认为自旋和轨道磁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观察到X射线吸收对线性二色性信号的影响，这与反铁磁体中没有X射线吸收磁性圆二色性信号形成鲜明对比。(2)V203中的反铁磁有序理论已知随着温度的降低而呈现金属-绝缘体转变。在低温反铁磁相中，晶体的对称性由高温相的双斜结构转变为单斜结构，表现出反映低对称性晶体结构的反常磁结构。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，发现交换相互作用的符号对晶格畸变敏感，并解释了磁有序性，而无需假设迄今为止提出的轨道有序模型。