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）在NAV_2O_5中的充电订单转换我们在NAV_2O_5中的35 K处发现了新颖的充电订单过渡，并与V_2O_5-FRAMEWORK（所谓的Trellis lattice）一起，通过共享VO_5 Square的边缘和角落形成。确定的电荷有序模式在A-B平面中具有V^<4+>和V^<5+>的锯齿形类型，沿C轴的AAA'A'的堆叠序列。我们发现在高压下出现了各种堆叠序列。所获得的相图与沮丧的自旋系统中Annni模型预测的魔鬼的花型相图理论。（2）对β-vanadium铜的研究，β-a___ <1/3> v_2o_5（a = li，a = li，na，na，ag，ag，ca，ca，ca，sr，pb）。八面体（V1）O_6和（V2）O_6和Square Pyramidal（V3）O_5，其中V1，V2和V3是独立的Ciystallographical vanadium位点。除A = Pb以外的所有化合物都显示了通过电荷订购进行的金属绝缘体跃迁。在高压下抑制了电荷有序相位，并且超导相似乎与A^+ - 化合物中的电荷有序相相邻。 A^+ - /a^<2+> - 化合物中的超导不传导性的存在表明超导性的最佳掺杂水平。（3）A站点有序的钙钛矿锰木岩rbamn_2o_6（rbamn_2o_6）（r = rar =稀数金属）。 A位置随机性对钙钛矿锰氧化物中电荷，轨道和自旋耦合现象的影响。首先，我们合成了中间化合物，缺氧的钙蛋白酶rbamn_2o_5与方形金字塔MNO_5。通过在相对较低的温度下氧化RBAMN_2O_5，我们成功地准备了RBAMN_2O_6。 RBAMN_2O_6显示出与普通无序锰岩不同的新型电荷，轨道和自旋耦合现象。