Organic Solid Laboratory, BNLMS, CMS &Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Institute of Condensed Matter Physics, College of Physics, Peking University, Beijing, 100871, P. R. China.
Sci Rep. 2014 Sep 23;4:6451. doi: 10.1038/srep06451.
As with quantum spin liquids based on two-dimensional triangular and kagome lattices, the two-dimensional honeycomb lattice with either a strong spin-orbital coupling or a frustrating second-nearest-neighbor coupling is expected to be a source of candidate quantum spin liquids. An ammonium salt [(C3H7)3NH]2Cu2(C2O4)32.2 containing hexagonal layers of Cu(2+) was obtained from solution. No structural transition or long-range magnetic ordering was observed from 290 K to 2 K from single crystal X-ray diffraction, specific heat and susceptibility measurements. The anionic layers are separated by sheets of ammonium and H2O with distance of 3.5 Å and no significant interaction between anionic layers. The two-dimensional honeycomb lattice is constructed from Jahn-Teller distorted Cu(2+) and oxalate anions, showing a strong antiferromagnetic interaction between S = 1/2 metal atoms with θ = -120 (1) K. Orbital analysis of the Cu(2+) interactions through the oxalate-bridges suggests a stripe mode pattern of coupling with weak ferromagnetic interaction along the b axis, and strong antiferromagnetic interaction along the a axis. Analysis of the magnetic susceptibility shows that it is dominated by a quasi-one-dimensional contribution with spin chains that are at least as well isolated as those of well-known quasi-one-dimensional spin liquids.
与基于二维三角和 kagome 晶格的量子自旋液体一样，具有强自旋轨道耦合或令人沮丧的第二近邻耦合的二维蜂窝晶格有望成为候选量子自旋液体的来源。从溶液中获得了含有六方层 Cu(2+)的铵盐[(C3H7)3NH]2Cu2(C2O4)32.2。从单晶 X 射线衍射、比热和磁化率测量来看，在 290 K 到 2 K 之间没有观察到结构转变或长程磁有序。阴离子层由厚度为 3.5 Å 的铵和 H2O 片层隔开，阴离子层之间没有明显的相互作用。二维蜂窝晶格由 Jahn-Teller 扭曲的 Cu(2+)和草酸盐阴离子构成，表现出 S = 1/2 金属原子之间的强反铁磁相互作用，θ = -120（1）K。通过草酸盐桥对 Cu(2+)相互作用的轨道分析表明，沿 b 轴具有弱铁磁相互作用的条纹模式耦合，而沿 a 轴具有强反铁磁相互作用。磁化率分析表明，它主要由准一维贡献主导，自旋链的隔离程度至少与那些众所周知的准一维自旋液体一样好。
