Thermal induced metal-insulator transition in the titanium oxides single crystals with a high melting point

高熔点氧化钛单晶中的热诱导金属-绝缘体转变

• 批准号: 10440110
• 负责人: IGA Fumitoshi
• 金额: $ 8.51万
• 依托单位: Hiroshima University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10440110/
• 关键词: Mott transiton; metal-insulator transition; orbital order; spin-charge separation; pressure effect; electrical resistivity; photoemission sepectroscopy; Perovskite-type oxide

We have studied the mechanism of a metal-insulator (M-I) transition by the magnetic, transport and thermal measurements of YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2 (x=0.3〜0.4) which exhibits inverse-Mott transition from a metallic state at low temperatures to a semiconducting one at high temperatures.1. Crystal growth and characterization: We have developed the method of growth for YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2 single crystals by using an image furnace. Oxygen contents of samples were determined by thermo-gravimetric analysis(TGA) . The results of TGA was used to obtain the best conditions for annealing under flowing oxygen.2. High-resolution photoemission spectroscopy : We have observed a clear M-I transition in the temperature-dependent photoemission spectra for x=0.39 consistent with transport measurements.3. Spin-charge separation : In a M-1 transition region, the significant difference in temperature dependences exist between magnetic .susceptibility and electrical resistivity. For a sample in the ferromagnetic region (x=0.05), we have found the stability of an orbital-ordered state a-s for x=0 by spin-polarized neutron diffraction.4. Future plans : Correlations among the charge , s pin and orbital in YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2 will be studied by the X-ray diffraction using synchrotron radiation and the spin-polarized neutron diffraction.

通过对Y_（21-x）Ca_（21-x）TiO_（22-x）Ca_（22-x）D_（23-x）D_（22-x）（x=0.3 ~ 0.4）的磁性、输运和热测量，我们研究了金属-绝缘体（M-I）转变的机制.晶体生长和表征：我们发展了用象炉生长Y_（21-x）O_（23）单晶的方法。通过热重分析（TGA）测定样品的氧含量。利用热重分析的结果确定了最佳的通氧退火条件.高分辨率光电子能谱：我们在x=0.39的温度依赖的光电子能谱中观察到了与输运测量一致的明显的M-I跃迁.自旋-电荷分离：在M-1过渡区，磁化率和电阻率随温度的变化存在显著差异。对于铁磁区（x=0.05）的样品，我们用自旋极化中子衍射发现了轨道有序态a-s（x=0）的稳定性.未来计划：用同步辐射X射线衍射和自旋极化中子衍射研究了Y_（21-x）O_（23）O

项目成果

M.Tsubota: "Low-field Magnetic Anisotropy in Mott-insulating Ferromagnet Y_<1-x>Ca_xTiO_3(x<0.1)"Physica B. (in press). (2000)

M.Tsubota：“莫特绝缘铁磁体 Y_<1-x>Ca_xTiO_3(x<0.1) 中的低场磁各向异性”Physica B.（出版中）。

T.Susaki: "Temperature-Dependent High-Resolution-Photoemission Study of YbB_<12>"Phys.Rev.Lett.. 82. 992-995 (1999)

T.Susaki：“YbB_<12> 的温度依赖性高分辨率光电发射研究”Phys.Rev.Lett.. 82. 992-995 (1999)

M. Tsubota et al.: "Low-Field Magnetic Anisotropy in Mott-Insulating Ferromagnet YィイD21-xィエD2CaィイD2xィエD2TiOィイD23ィエD2(x<0.1)"Physica B. (in press). (2000)

M. Tsubota 等人：“莫特绝缘铁磁体 YD21-xD2CaD2xD2TiOD23D2(x<0.1) 中的低场磁各向异性”Physica B. (in (2000)

M.Arita: "Temperature-Dependent High-Resolution Photoemission Study of Y_<1-x>Ca_xTiO_3"Rev.High Pressure Sci.Technology. 38. 206-208 (1999)

M.Arita：“Y_<1-x>Ca_xTiO_3 的温度依赖性高分辨率光电发射研究”Rev.高压科学技术。

F.Iga: "Effects of High pressure and High-Magnetic Field on the Energy Gap in a Kondo Semiconductor YbB_<12>"Jpn.J.Appl.Phys.. series 11. 88-90 (1999)

F.Iga：“高压和高磁场对近藤半导体 YbB_<12> 能隙的影响”Jpn.J.Appl.Phys.. 系列 11. 88-90 (1999)