新型 S=1/2 kagome 反铁磁材料的单晶生长和磁性研究

自旋S=1/2 kagome晶格由于具有最强的几何阻挫和量子涨落效应，是最有可能出现量子自旋液体基态的体系。然而到目前为止只有少数几种体系被发现是量子自旋液体材料。呼吸型kagome晶格也可以稳定自旋液体态，但是尚未发现由Cu离子构成的物质。为了寻找更多的S=1/2 kagome量子自旋液体材料，本项目利用水热法拟从以下几个方面设计合成多种新型S=1/2 kagome体系：1）在MgCu3(OH)6Cl2中将Cl离子替换成Br或NO3离子；2）在ZnCu3(OH)6XX’(XX'=FCl,FBr)中将Zn离子替换成Mg离子；3）以前期合成的Cu基呼吸型kagome材料为中心，替换非磁性阳离子和阴离子基团。以这些材料为研究对象，在低温下开展磁学和热力学性质表征，总结归纳基态磁性随结构参数的变化规律，建立基态磁性的量子相图，为寻找新型S=1/2 kagome量子自旋液体材料提供实验依据。

S=1/2 kagome lattice is the most promising system to host quantum spin liquid (QSL) ground state on account of the strongest geometrical frustration and quantum fluctuations. However, only a few materials are discovered to be QSL candidates. Breathing kagome lattice is found to be an alternative way to stabilize QSL state, but no Cu-based compounds have been reported so far. To search for more S=1/2 kagome QSL candidates, this project will synthesize several novel S=1/2 kagome materials using hydrothermal technique from the following points: 1) replacing Cl by Br or NO3 anion in MgCu3(OH)6Cl2; 2) replacing Zn by Mg cation in ZnCu3(OH)6XX’(XX'=FCl,FBr); 3) changing the non-magnetic cations or anionic groups in our pre-grown Cu-based breathing kagome compound. Based on the above single crystals, we will perform the magnetic and thermodynamic characterizations at low temperatures in order to study the relation between the ground state magnetism and the structural parameters, establish the phase diagram of the ground state magnetism, and make an experimental support for discovering novel S=1/2 kagome QSLs in future.