硫属尖晶石体系阻挫相关物性研究

Due to the existence of spin and orbital frustration, chalcogenide spinels display exotic behaviors, such as spin ice, spin orbital liquid, orbital glass and etc.. Accompanied by strong coupling among spin, charge, orbital and lattice degrees of freedom, this system also shows fascinating phenomena, for example multiferroics, magnetostriction, negative thermal expansion, spin driven structural transition and so on. However, many basic physical properties in this system are still unclear, especially the origin of complex spin and orbital order. On the basis of our former work, this project will be carried out by focusing on the spin and orbital frustration in chalcogenide spinels. We will modulate the spin and orbital order via high magnetic field, combination of external pressure and chemical pressure. Through this project, we will try to understand how the spin, charge, orbital and lattice coupling is influenced by the frustration, therefore construct the correlation between physical properties and different ordering states. The implement of the project will be beneficial not only for exploring novel functional materials, e.g., multiferroic and magnetostrictive materials, but also for better understanding the strong coupling of spin-orbital-lattice in the frustrated system.

硫属尖晶石体系存在自旋和轨道阻挫现象，表现出诸如自旋冰、自旋-轨道液态和轨道玻璃态等复杂的行为，伴随着自旋、轨道、电荷、晶格等多种自由度的耦合，还表现出多铁性、磁致伸缩、负热膨胀、磁致结构转变等丰富的物理效应，目前该体系中许多基本的物理问题如复杂的自旋、轨道序的成因还不清楚。本项目将在已有工作基础上，着重于过渡金属硫族尖晶石体系的自旋、轨道阻挫现象，通过外加磁场、外加压力与化学压力相结合等手段调节体系自旋、轨道序的形成过程，研究阻挫对自旋、轨道、电荷以及晶格等自由度的制约机理，以建立宏观物性与不同有序态之间的关联；本项目的顺利完成，将有助于探寻新型功能材料，如多铁性材料、磁致伸缩材料等，并有助于阻挫体系自旋-晶格-轨道强耦合机制的深入理解。

硫属尖晶石体系存在自旋和轨道阻挫现象，表现出诸如自旋冰、自旋-轨道液态和轨道玻璃态等复杂的行为，伴随着自旋、轨道、电荷、晶格等多种自由度的耦合，还表现出多铁性、磁致伸缩、负热膨胀、磁致结构转变等丰富的物理效应。本项目着重于过渡金属硫族尖晶石体系的自旋、轨道阻挫现象，主要研究成果如下：1. 在硫属尖晶石磁阻挫材料ZnCr2Se4中揭示了磁场驱动的量子临界现象；2. 揭示了ZnCr2Se4中负热膨胀和磁致伸缩效应起因于磁交换能与晶格弹性能之间的竞争；3. 研究了硫属尖晶石体系CdCr2S4单晶样品的多铁性以及HgCr2S4、FeCr2S4的压力效应；4. 发现了若干压力诱导超导电性、拓扑相变等的新现象。在本项目资助下，项目负责人以通讯作者共发表SCI论文32篇，其中PNAS 1 篇、Phys. Rev. Lett. 2篇、npj Quant. Mater. 2篇、Phys. Rev. B 9篇、Adv. Electron. Mater. 2篇、Phys. Rev. Mater. 2篇。还应邀为国际英文专著《Magnetic Spinels - Synthesis, Properties and Applications》（InTech，2017）撰写了一个章节。