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

基本信息

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

项目摘要

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.

一种新颖的库酸盐Volborthite，Cu_3v_2O_7（OH）_2 _2H_2O，包含s-1/2（Cu^<2+>旋转）Kagome（如晶格），是通过磁敏感性，特定热量和V NMR测量值进行的。尽管在Cu旋转之间旋转二维Kagome网络的CU旋转之间，但仍检测到长距离顺序或旋转的单线基态的符号下降至1.8 K。建议volborthite代表一个接近量子的系统，几乎是经典的远程和量子无序阶段之间的量子临界点。BACU_2（SI__ <1-x> ge_x）_2O_7，包括瓦楞纸式的CU-O链，已被发现是旋转的Cu-O链，与290 K in 29 Keisenberg System是Spin-1D Heisenberg System是290 K. （x = l）。链相互作用还显示出显着的组成依赖性，从铁磁（x = 0）到抗反磁性（x = l）不同。这些强大的组成依赖性已被发现导致了丰富的磁相图。在边缘共享CUO_2链上掺杂的孔几乎是由于几乎正交的Cu-O-CU键所定位的。因此，仅在低温下生存自旋程度，有时会出现异常的量子磁性。准二维纯氧化物CA__ <1-x> cuo_ <2+d>和sr_ <14> cu_ <24> o_ <41>均包含25-50％的孔掺杂边缘 - 边缘 - 边缘cuO2链，是通过均匀的磁性敏感性和一系列多晶的金属对均匀的热量测量的均匀的磁化剂和特定的热量测量，并具有一系列的多晶剂，以及一系列的多晶元素。 Most of spins are dimerized always in Sr_<14>Cu_<24>O_<41>, while, in contrast, antiferromagnetic chains made of almost 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几何挫败感和特殊的Cu-O-CU键角为95。