Preparation and physical properties of single crystals of Hg-based cupric oxide superconductors

Hg基氧化铜超导体单晶的制备及物理性能

• 批准号: 10640340
• 负责人: HIROI Zenji
• 金额: $ 1.79万
• 依托单位: University of Tokyo (1999)Kyoto University (1998)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 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-10640340/
• 关键词: high-Tc superconductors; single-crystal growth; Hg-based Cu oxides; hydrothermal synthesis; 高温超伝導; 銅酸化物; 単結晶; 臨界電流密度

A novel cuprate Volborthite, Cu_3V_2O_7(OH)_2・2H_2O, containing an S-1/2 (Cu^<2+> spin) kagome like lattice is studied by magnetic susceptibility, specific heat, and V NMR measurements. Signs for neither long-range order nor spin-gapped singlet ground states are detected down to 1.8 K, in spite of large antiferromagnetic couplings of-100 K between Cu spins fomrning a two-dimensional Kagome like network. It is suggested that Volborthite represents a system close to a quantum critical point between classical long-range ordered and quantum disordered phases.BaCu_2(Si_<1-x>Ge_x)_2O_7 comprising corrugated Cu-O chains has been found to be a spin-1/2 1D Heisenberg system with a linearly tunable exchange interaction from 290 K (x=0) to 580 K (x=l). The interchain interaction also shows a remarkable composition dependence varying from ferromagnetic (x=0) to antifer-romagnetic (x=l). These strong composition dependences have been found to lead to a rich magnetic phase diagram.Holes doped on edge-sharing CuO_2 chains are almost localized because of nearly orthogonal Cu-O-Cu bonds. Consequently, only spin degrees of freedom survive at low temperature, which sometimes presents unusual quantum magnetism. Quasi-one-dimensional cupric oxides Ca_<1-x>CuO_<2+d> and Sr_<14>Cu_<24>O_<41>, both containing 25-50% hole-doped edge-sharing CuO2 chains, are studied by uniform magnetic susceptibility and specific heat measurements on a series of polycrystalline samples with controlled metal and oxygen contents. Most of spins are dimerized always in Sr_<14>Cu_<24>O_<41>, while, in contrast, antiferromagnetic chains made of nearly 50% spins exist with the remainder forming dimers of variable density in Ca_<1-x>CuO_<2+d>.A two-sublattice model is proposed by considering that the nearest-neighbor couplings are negligibly small, due to both geometrical frustration and the special Cu-O-Cu bond angle of-95.

通过磁化率、比热和 V 核磁共振测量研究了一种新型铜酸盐伏硼铁矿 Cu_3V_2O_7(OH)_2·2H_2O，其含有 S-1/2 (Cu^<2+> 自旋) kagome 状晶格。尽管 Cu 自旋之间存在约 100 K 的大反铁磁耦合，形成了二维 Kagome 状网络，但在低至 1.8 K 的温度下，都没有检测到长程有序或自旋间隙单线态基态的迹象。研究表明，伏硼铁矿代表了一个接近经典长程有序相和量子无序相之间量子临界点的体系。由波纹状Cu-O链组成的BaCu_2(Si_<1-x>Ge_x)_2O_7被发现是一个自旋1/2 1D海森堡体系，具有从290 K (x=0)到580 K线性可调的交换相互作用 (x=l)。链间相互作用还表现出显着的成分依赖性，从铁磁（x = 0）到反铁磁（x = 1）。这些强烈的成分依赖性已被发现导致丰富的磁性相图。由于几乎正交的Cu-O-Cu键，掺杂在共享边缘的CuO_2链上的空穴几乎是局域化的。因此，只有自旋自由度能够在低温下生存，这有时会呈现出不寻常的量子磁性。通过对一系列金属和氧含量受控的多晶样品进行均匀磁化率和比热测量，研究了准一维氧化铜Ca_<1-x>CuO_<2+d>和Sr_<14>Cu_<24>O_<41>，两者均含有25-50%空穴掺杂共边CuO2链。 Sr_<14>Cu_<24>O_<41> 中大多数自旋总是二聚化，而相反，由近 50% 自旋组成的反铁磁链存在，其余部分形成 Ca_<1-x>CuO_<2+d> 中密度可变的二聚体。 几何挫折和特殊的Cu-O-Cu键角为-95。

项目成果

T.Yamada: "Spin-1/2 Heisenberg antiferromagnetic chains in the frustrated spinel lattice of GeCu_2O_4"J.Phys.Soc.Jpn.. 69-5. 1477-1483 (2000)

T.Yamada：“GeCu_2O_4 受挫尖晶石晶格中的 Spin-1/2 海森堡反铁磁链”J.Phys.Soc.Jpn.. 69-5。

Z.Hiroi: "La_<1-x>Sr_xCuO_<2.5> representing a hole-doped spin ladder system"Physica B. 259-261. 1034-1035 (1999)

Z.Hiroi：“代表空穴掺杂自旋梯系统的La_<1-x>Sr_xCuO_<2.5>”Physica B.259-261。

S.Sugai: "Spin Gap at the Phase Transition between Spin Liquid and Long-Range Ordered State in La_<1x>Sr_xCuO_<25>" Rev.High Pressure Sci.Technol. 7. 571-573 (1998)

S.Sugai：“La_<1x>Sr_xCuO_<25> 中自旋液体与长程有序态之间相变的自旋间隙”Rev.高压科学技术。

T.Yamada, Z.Hiroi, M.Takano, M.Nohara and H.Takagi: "Spin-1/2 Heisenberg antiferromagnetic chains in the frustrated spinel lattice of GeCu_2O_4"J.Phys.Soc.Jpn. 69 (5). 1477-1483 (2000)

T.Yamada、Z.Hiroi、M.Takano、M.Nohara 和 H.Takagi：“GeCu_2O_4 受抑尖晶石晶格中的 Spin-1/2 海森堡反铁磁链”J.Phys.Soc.Jpn。

T.Yamada: "Spin-1/2 Heisenberg antiferromagnetic chains in the frustrated spinel lattice of GeCu_2O_1"J.Phys.Soc.Jpn,. (in press).

T.Yamada：“GeCu_2O_1 受挫尖晶石晶格中的 Spin-1/2 海森堡反铁磁链”J.Phys.Soc.Jpn，。