The study of electric and crystal structural changes on the strongly correlated electron oxide under high pressure

高压下强相关电子氧化物的电学和晶体结构变化研究

• 批准号: 11450239
• 负责人: YAMADA Yuh
• 金额: $ 7.62万
• 依托单位: Shimane University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11450239/
• 关键词: The strongly correlated electron oxide; The effects of pressure; High T_2 oxide superconductor; The Rietveld refinement; The structural analysis; 強相関酸化物; 高圧X線回折; マキシマムエントロピー法

We have investigated the electric and crystal structural changes on the strongly correlated electron oxide and alloys under high pressure. The results are explained in the following.(1) We have successfully grown single crystals of PrBa_2Cu_4O_8 (Pr124) by a flux method under high-pressure oxygen gas. The structure data of a Pr124 single crystal were taken by using a four-circle diffractometer and the structure was refined by full matrix least-square structure refinements. All z-positional parameters are essentially the same between the single crystal and the polycrystalline Pr124. The temperature dependence of resistivity of Pr124 single crystals did not exhibit superconductivity, at least down to 2 K. Resistivity along the b- axis showed a highly conductive behavior, of which the origin is attributed to the double-chain site because of the large anisotropy between the resistivities along a- and b- axes.(2) The RuSr_2GdCu_2O_8 oxide exhibits the superconducting transition at about 40K and ferromagnetic order at about 130K. The pressure dependence of the superconducting and ferromagnetic transition temperature of this sample was measured. The superconducting transition temperature was scarcely varies under pressure. The ferromagnetic transition temperature increases with increasing pressure.(3) Magnetization, electrical resistivity and specific heat measurements have been made on Heusler-type Fe_2VAl compound. The electrical resistivity shows semiconductor-like negative temperature dependence. We suggested that this compound should be a semimetal with a pseudogap in the density of states at the Fermi level.

我们研究了强相关电子氧化物和合金在高压下的电学和晶体结构变化。结果如下：(1)我们在高压氧气下采用熔剂法成功生长了PrBa_2Cu_4O_8(Pr124)单晶。使用四环衍射仪获取Pr124单晶的结构数据，并通过全矩阵最小二乘结构精修来精修结构。单晶和多晶 Pr124 之间的所有 z 位置参数基本相同。 Pr124单晶电阻率的温度依赖性没有表现出超导性，至少低至2 K。沿b轴的电阻率表现出高导电行为，其根源归因于双链位点，因为沿a轴和b轴的电阻率之间存在较大的各向异性。(2)RuSr_2GdCu_2O_8氧化物在约 40K，铁磁阶约为130K。测量了该样品的超导和铁磁转变温度的压力依赖性。超导转变温度在压力下几乎不变化。铁磁转变温度随压力的增加而升高。(3)对Heusler型Fe_2VAl化合物进行了磁化强度、电阻率和比热的测量。电阻率显示出类似半导体的负温度依赖性。我们认为这种化合物应该是一种半金属，在费米能级的态密度上具有赝能隙。

项目成果

A,Matsushita., K,Akagi., G,Piao., Y,Yamada.: "C_nF_<2n+2> intercalation in polyacetylene"Synthetic Metals. 119. 377-378 (2001)

A，Matsushita.，K，Akagi.，G，Piao.，Y，Yamada.：“聚乙炔中的C_nF_<2n 2>插层”合成金属。

A. Matsushita, T. Naka, Y. Takano, T. Takeuchi, T. Shishido and Y. Yamada: "Pseudogap and transport properties in Fe_<3-x>V_xAl_y (x = 0.5-1.05 ; y = 0.95, 1.05)"Phys. Rev. B. 65. 75204 1-6 (2002)

A. Matsushita、T. Naka、Y. Takano、T. Takeuchi、T. Shishido 和 Y. Yamada：“Fe_<3-x>V_xAl_y (x = 0.5-1.05；y = 0.95, 1.05) 中的赝能隙和输运特性

T.Kishi, Y.Yamada et al.: "Structure of epitaxial BiPbSrCuO films grown at low temperatures"Physica C. 357-360. 1394-1398 (2001)

T.Kishi、Y.Yamada 等人：“低温生长的外延 BiPbSrCuO 薄膜的结构”Physica C. 357-360。

S.Horii, Y.Yamada et al.: "Growth and Transport Property of Single Crystal PrBa_2Cu_4O_8"Advances in Superconductivity XI. XI. 89-92 (1999)

S.Horii、Y.Yamada 等：“单晶 PrBa_2Cu_4O_8 的生长和输运特性”超导进展 XI。

K.Soda, Y.Yamada et al.: "High-resolution photoelectron spectroscopy of Heusler-type Fe_2VAl alloy"J. Synchrotron Radiation. (in press). (2002)

K.Soda, Y.Yamada等：“Heusler型Fe_2VAl合金的高分辨率光电子能谱”J.