The Theory of Material Design for Transition Metal Oxides

过渡金属氧化物材料设计理论

基本信息

批准号：
09440129
负责人：
MAEKAWA Sadamichi
金额：
$ 8.32万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 2000
项目状态：
已结题

项目摘要

In transition metal oxides, the separation of internal degrees of freedom of election, spin charge orbital, occurs due to the strong electron correlation, thus, the degrees behave independently and complete each other. As a result, symmetry breaking quantum states (phases) appear. Than order to make the material design possible, it is of primary importance to construct the theory of observation of the order parameters of the degrees and their elementary excitations. In this research project, we have examined the possibility of observing the elementary excitations of spin and charge, i.e., spinons and holons, and succeeded in observing them, for the first time, in the angle-resolved-photoemission spectroscopy (APRES) experiment in a one-dimensional cuprate, SrCuO_2. This work has been done in collaboration with the experimental groups in University of Tokyo and Stanford University. Also developed was the theory of observation of orbital ordering by using resonant X-ray scattering (RXS) … More . The elementary excitation in the Raman scattering experiment. It was shown that the orbital governs the transport (charge degree) and magnetic (spin degree) properties in transition metal oxides. In La_<0.88>Sr_<0.12>MnO_3, the metallic state shows weak ferromagnetism in the temperature (T) region of 145<T<171K.However, below 145K, the state changes to the insulating one with strong ferromagnetism. It was shown that the occurrences of two ferromagnetic states and metal-insulator transition are caused by the orbital degree : At high temperatures, the orbital fluctuation induces entropy and stabilizes the metallic state. However, at low temperatures, the orbital ordering occurs and the energy decreases. The orbital ordering brings about the superexchange interaction, which induces the strong ferromagnetism. The orbital ordering in this compound was detected in RXS and analyzed by using the theory mentioned above.In this research project, the theory of the internal degrees of freedom of electron, spin charge orbital, in transition metal oxides was developed and the basis of the material design was constructed. Less

在过渡金属氧化物中，由于强电子相关性，内部选举自由度（自旋电荷轨道）发生分离，因此，这些自由度表现独立且彼此完整，结果出现对称性破坏的量子态（相）。为了使材料设计成为可能，最重要的是构建度数及其基本激发的有序参数的观察理论。在这个研究项目中，我们研究了观察自旋基本激发的可能性。并充电，即自旋子和完整子，并在一维铜酸盐SrCuO_2的角分辨光电子能谱（APRES）实验中首次成功观察到它们。这项工作是与大学实验组合作完成的。东京和斯坦福大学还开发了利用共振 X 射线散射 (RXS) 观察轨道有序的理论……更多拉曼散射实验中的基本激发。在La_<0.88>Sr_<0.12>MnO_3中，轨道控制着过渡金属氧化物的输运（电荷度）和磁性（自旋度）性质，金属态在145<T<171K的温度（T）范围内表现出弱铁磁性。然而，在145K以下，状态转变为具有强铁磁性的绝缘状态，这表明出现了两种情况。铁磁态和金属-绝缘体转变是由轨道度引起的：在高温下，轨道涨落会引起熵并稳定金属态，但在低温下，会发生轨道有序化，轨道有序化会导致能量降低。超交换相互作用，在RXS中检测到了该化合物中的强铁磁性，并利用上述理论进行了分析。在本研究项目中，内度理论。开发了过渡金属氧化物中的电子自由度、自旋电荷轨道，并构建了材料设计的基础。