权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Charge, Spin and Orbital States of Transition Metal Oxides with Square Pyramidal Coordination

方锥配位过渡金属氧化物的电荷、自旋和轨道态

基本信息

批准号：
14340205
负责人：
UEDA Yutaka
金额：
$ 9.09万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

(1)Charge order transition in NaV_2O_5.We found novel charge order transition at 35 K in NaV_2O_5 with the V_2O_5-framework, so-called trellis lattice, formed by sharing the edges and corners of VO_5 square pyramids. The determined charge ordered pattern has a zigzag type of V^<4+> and V^<5+> in the a-b plane and the stacking sequence of AAA'A' along the c-axis. We found that various stacking sequences appear under high pressure. The obtained phase diagram is very similar to the devil's flower type phase diagram theoretically predicted from ANNNI model in frustrated spin system.(2)Study on β-vanadium bronzes, β-A_<1/3>V_2O_5 (A=Li,Na,Ag,Ca,Sr,Pb).The V_2O_5-framework of β-A_<1/3>V_2O_5 is formed by octahedral (V1)O_6 and (V2)O_6 and square pyramidal (V3)O_5, where V1, V2 and V3 are independent ciystallographical vanadium sites. All compounds except A=Pb show metal-insulator transitions accompanied by the charge ordering. The charge ordered phase is suppressed under high pressure and the superconducting phase appears adjacent to the charge ordered phase in A^+-compounds. The presence/absence of superconductivity in A^+-/A^<2+>-compounds indicates an optimum doping level for the superconductivity.(3)The A-site ordered perovskite manganites, RBaMn_2O_6 (R=rare earth metal).We successfully synthesized the A-site ordered perovskite manganites, RBaMn_2O_6, which have been desired to study the A-site randomness effect on the charge, orbital and spin coupled phenomena in perovskite manganese oxides. At first we synthesized the intermediate compounds, oxygen-deficient perovskites RBaMn_2O_5 with square pyramidal MnO_5. By oxidizing RBaMn_2O_5 at relatively low temperature about 600 K, we succeeded in preparing RBaMn_2O_6. RBaMn_2O_6 shows novel charge, orbital and spin coupled phenomena different from those of ordinary disordered manganites.

（1）NaV_2O_5中的电荷有序跃迁。我们在35 K时发现了新的电荷有序跃迁，它具有V_2O_5-骨架结构，即所谓的格子结构。在a-b平面上V^<4+>和V^<5+>为锯齿型，沿c轴为沿着排列的AAA 'A'。我们发现在高压下会出现各种各样的堆积序列。所得相图与ANNNI模型理论预言的阻挫自旋系统的魔鬼花型相图十分相似。（2）β-A_（1/3）V_2O_5（A=Li，Na，Ag，Ca，Sr，Pb）的研究β-A_（1/3）V_2O_5的V_2O_5骨架由八面体（V1）O_6、（V2）O_6和四方锥（V3）O_5构成，其中V1、V2和V3是独立的晶体学钒位。除A=Pb外，所有化合物均表现出金属-绝缘体相变，并伴有电荷有序化。在高压下，电荷有序相被抑制，在A^+-化合物中，超导相出现在电荷有序相附近。A^+-/A^<2+>-化合物中超导电性的存在/不存在表明了超导电性的最佳掺杂水平。（3）A位有序钙钛矿锰氧化物RBaMn_2O_6（R=稀土金属）我们成功地合成了A位有序钙钛矿锰氧化物RBaMn_2O_6，这是研究A位无规性对钙钛矿锰氧化物中电荷、轨道和自旋耦合现象的影响所需要的。首先，我们以四方锥MnO_5为原料合成了缺氧钙钛矿RBaMn_2O_5。在600 K左右的较低温度下氧化RBaMn_2O_5，成功地制备出RBaMn_2O_6。RBaMn_2O_6具有不同于普通无序锰氧化物的电荷、轨道和自旋耦合现象。