自旋二聚体ACuX2(A=Mg,Cd,Hg;X=SO4,SeO3,TeO3)的单晶生长和磁性研究

具有自旋能隙的二聚体材料由于在外磁场作用下可以发生磁振子玻色—爱因斯坦凝聚（BEC）现象因而一直是凝聚态物理领域的研究热点，然而具有孤对电子的亚硒/亚碲酸盐二聚体在磁性方面的研究却还处于起步阶段。最近人们发现二聚体材料HgCu(SeO3)2和CdCu(SeO3)2很可能是一类新型的自旋能隙材料。为了探究孤对电子对磁交换作用及磁性质的影响，本项目将以二聚体ACuX2(A=Mg,Cd,Hg;X=SO4,SeO3,TeO3)体系为研究对象，在低温强磁场下开展各向异性的磁学和热力学表征，揭示非磁性阳离子半径和阴离子基团对磁性质的影响。以水热合成方法为主要手段，实现毫米尺寸高品质单晶样品的生长，为各向异性的物性表征提供样品保障。通过本项目的开展，有望对二聚体ACuX2型亚硒/亚碲酸盐的磁性质形成全面系统的认识，为将来设计合成新型的自旋能隙材料提供依据，并且为磁振子BEC的研究打开一个全新的领域。

Study on the spin-gapped dimer compounds is a hot topic and has atrtacted great attention due to the exotic magnon Bose-Einstein condensation (BEC) phenomenon under magnetic field. However, magnetism is known little for the dimerized selenites/tellurites in the presence of lone-pair electrons. Recently chemists discovered that HgCu(SeO3)2 and CdCu(SeO3)2 might be possible spin-gapped candidates. To reveal the influence of lone-pair electrons on the magnetic exchange and properties, this project will focus on the dimerized ACuX2(A=Mg,Cd,Hg;X=SO4,SeO3,TeO3) family to study the replacement effect of nonmagnetic cation and anionic group on the magnetism by means of anisotropic susceptibility and specific heat measurement at low temperatures and in high magnetic fields. Millimeter-size single crystals with high quality will be grown using hydrothermal technique which is the important guarantee for the subsequent anisotropic experiments. Through this project, we try to understand deeply about the magnetic properties of dimerized ACuX2 selenites/tellurites and provide helpful guides to design and synthesize new spin-gapped materials in the future. More importantly, we hope to open a new field to explore the magnon BEC in the selenites/tellurites.