Correlation Phenomena among electric, magnetic and mulitiple dipoles in ferroelectric oxides

铁电氧化物中电、磁和多偶极子之间的相关现象

• 批准号: 16340094
• 负责人: MORI Shigeo
• 金额: $ 7.55万
• 依托单位: Osaka Prefecture University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16340094/
• 关键词: Ferroelectric Oxides; magnetoelectric effect; manganites; magnetocapacitance effect; synchrotron x-ray diffraction; electron diffraction; multiferroic materials; 放射光x線回折実験; 電子線回折実験

Effective interaction between charges and spins in solids are often quite different from the fundamental laws in electrodynamics, which gives rise to unusual phenomena. The coupling between static electric and magnetic dipoles, which are observed in magnetic ferroelectric materials (so-called multiferroic materials), is a fascinating effect interesting both for its fundamental physics and potential technological applications. In our research project, we mainly focused on the exploration of novel phenomena such as the gigantic electromagnetic effect in ferroelectric magnetic oxides, which are caused by effective interaction among charge, spin and orbital degrees of freedom, and elucidated their physical origins of the phenomena. The main research achievements are as follows.(1)We found the phenomena that an external magnetic field induces and modifies ferroelectric states in DyMn_2O_5. This compound shows successive phase transitions between 43K and 4K, accompanying three ferroelectric … More phases. We obtained the electric phase diagram for DyMn_2O_5 in the plane of temperature and magnetic field.(2)We found that the charge-ordered (CO) structure in LuFe_2O_4 is characterized by the modulated structure with the wave vector of q=1/3[1-13/2] and the average size of the CO domains can be estimated to be about 10-20nm. On the contrary, the Cu^<2+> (Co^<2+>) substitution in LuFe_2O_4 destroyed the CO structure drastically and induced characteristic local lattice distortion, which gives rise to characteristic diffuse scattering. High-resolution lattice images in LuFeCuO_4 revealed that there exist nano-scale clusters, which are characterized as the short-range ordering of the Fe^<3+> and Cu^<2+> ions on the triangular lattice. The magnetic measurements revealed that LuFeCu(Co)O_4 exhibits a magnetic transition around 45K(80K), which is much lower than the magnetic transition temperature of 250K in LuFe_2O_4.(3)We analyzed theoretically the electronic structure and dielectric property in a layered oxide RFe_2O_4. Charge frustration in paired-triangular lattices allows a charge imbalance with out inversion symmetry, i.e. the electric polarization. Spin frustration induces reinforcement of this polar CO by a magnetic ordering. We also analyze an orbital model for the Fe ion which does not show a conventional long-range order. Less

固体中电荷和自旋之间的有效相互作用通常与电动力学的基本定律有很大不同，这会产生不寻常的现象。在磁性铁电材料（所谓的多铁材料）中观察到的静电偶极子和磁偶极子之间的耦合是一种令人着迷的效应，无论其基础物理还是潜在的技术应用都令人感兴趣。在我们的研究项目中，我们主要致力于探索由电荷、自旋和轨道自由度之间的有效相互作用引起的铁电磁性氧化物中的巨大电磁效应等新现象，并阐明了这些现象的物理起源。主要研究成果如下：(1)发现了外磁场诱导和改变DyMn_2O_5铁电态的现象。该化合物显示出 43K 和 4K 之间的连续相变，并伴有三个铁电相。我们得到了DyMn_2O_5在温度和磁场平面上的电相图。(2)我们发现LuFe_2O_4中的电荷有序(CO)结构具有波矢q=1/3[1-13/2]的调制结构特征,CO域的平均尺寸约为10-20nm。相反，LuFe_2O_4中的Cu^<2+>(Co^<2+>)取代极大地破坏了CO结构并引起特征局部晶格畸变，从而产生特征漫散射。 LuFeCuO_4的高分辨率晶格图像表明存在纳米级团簇，其特征是三角晶格上Fe^<3+>和Cu^<2+>离子的短程有序排列。磁测量结果表明,LuFeCu(Co)O_4在45K(80K)左右表现出磁转变,远低于LuFe_2O_4 250K的磁转变温度。(3)对层状氧化物RFe_2O_4的电子结构和介电性能进行了理论分析。成对三角形晶格中的电荷挫败允许电荷不平衡，而没有反演对称性，即电极化。自旋挫败通过磁排序诱导这种极性 CO 的强化。我们还分析了铁离子的轨道模型，该模型没有显示出传统的长程有序。较少的

项目成果

Dilution effects in classical and quantum orbital systems

经典和量子轨道系统中的稀释效应

• 发表时间: 2007
• 期刊: J. Magn. Magn. Mater 310
• 作者: T.Tanaka;M.Matsumoto;S.Ishihara
• 通讯作者: S.Ishihara

Electron-Phonon Interaction in Correlated Cuprate Superconductors

相关铜酸盐超导体中的电子-声子相互作用

• 发表时间: 2006
• 期刊: Jour. Phys. Chem. Solids 67
• 作者: S.Ishihara;N.Nagaosa
• 通讯作者: N.Nagaosa

Magnetoelectric phase diagrams of orthorhombic RMnO3 (R=Gd, Tb, and Dy)

• DOI: 10.1103/physrevb.71.224425
• 发表时间: 2005-06-01
• 期刊: PHYSICAL REVIEW B
• 影响因子: 3.7
• 作者: Kimura, T;Lawes, G;Ramirez, AP
• 通讯作者: Ramirez, AP

Structural phase transition and dielectric anomalies in YFe_2O_<4->

YFe_2O_<4->中的结构相变和介电异常

• 发表时间: 2005
• 期刊: J.Korea Physical Society 46, No.1
• 作者: Y.Horibe;K.Kishimoto;S.Mori;N.Ikeda
• 通讯作者: N.Ikeda

Nanoscale Ferromagnetism in phase separated manganites

相分离锰酸盐中的纳米级铁磁性

• 发表时间: 2007
• 期刊: Journal of Magnetism and Magnetic Materials 310
• 作者: Yukio Watanabe;Mizuki Yamato;Yousuke Urakami;Daisuke Matsumoto;T.Arima;S.Mori
• 通讯作者: S.Mori