Charge ordering and metal-insulator transition in mixed-valence transition metal oxcides

混合价过渡金属氧化物中的电荷排序和金属-绝缘体转变

基本信息

批准号：
15540332
负责人：
OHAMA Tetsuo
金额：
$ 1.6万
依托单位：
Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540332/
关键词：
NMR electron correlation magnetic structure metal-insulator transition 磁気秩序軌道状態

项目摘要

Developement of NMR spectrometerIn this research, we need an NMR spectrometer with wide band width to observe the resonance in magnetically ordered states. We developed a spectrometer for 5 to 220MHz.Charge ordering in vanadatesWe studied the spin dynamics in the uniform state in a charge ordering system α'-NaV_2O_5. We observed low-dimensional behavior in the nuclear relaxation ; it agrees with our expectation from the crystal structure. The further understanding of this behavior and effects of charge fluctuation is a future problem.Ferromagnetism in vanadatesIn order to study the orbital and spin states and the magnetic excitations in insulating magnetic ordered states on frustrated lattices, we studied a vanadates with the pyrochlore structure Lu_2V_2O_7. We observed NMR spectra for Lu and V sites in the ferromagnetic state to investigate the orbital state. The experiments and the data analysis are in progress.Antiferromagnetism in f-electron systemsIn order to study magnetic ordering in metals and its relation with metal-insulator transition, we studied a metallic antiferromagnet UNiGa_5. We analyzed NMR spectra for the ligand Ga sites in the antiferromagnetic and paramagnetic phases and determined the quadrupole parameters and the internal fields at the Ga sites.We proposed a new NMR analysis of magnetic structures with magnetic space group and the representation analysis of magnetic structure and applied it to UNiGa_5 (published in Phys.Rev.B).

NMR光谱计的开发这项研究，我们需要具有宽带宽度的NMR光谱仪，以观察磁有序状态的共振。我们开发了一个用于5至220MHz的光谱仪。瓦纳德瓦茨韦（Vanadateswe）中的电荷顺序研究了均匀状态下的旋转动力学，以充电订购系统α'-nav_2o_5研究。我们观察到核松弛中的低维行为。它与我们对晶体结构的期望一致。对电荷波动的这种行为和影响的进一步理解是未来的问题。钒酸盐中的Ferromagnetism为了研究轨道和旋转状态和旋转状态以及在沮丧的晶格上绝缘磁有序状态的磁兴奋，我们研究了pyrochlore结构LU_2V_2V_2O_7。我们观察到铁磁状态的LU和V位点的NMR光谱研究轨道状态。实验和数据分析正在进行中。f-电子系统中的抗铁磁性为了研究金属中的磁有序及其与金属 - 绝缘体过渡的关系，我们研究了金属抗Fiferromagnet uniga_5。我们分析了抗铁磁和顺磁性阶段中配体GA位点的NMR光谱，并确定了GA位点的四极参数和内部磁场。我们提出了与磁性空间组的磁性结构进行的新的NMR分析，并将其应用于Uniga_5（Uniga_5（Uniga_5（Uniga_5））（在Pharterned in Pharterned.red.rev.b.rev.b.rev.b）中。