从阻挫到自旋手性

Geometric frustration of interacting spin systems is the driving force of a variety of fascinating phenomena in low-dimensional magnetism. Perturbation to the subtle spin frustration may induce the change of spin structure, resulting in the formation of topologically distinct spin texture, such as spin chirality recognized as promising for future applications in quantum computing and information storage. The objective of the present proposal is to produce and characterize new spin chirality systems derived from highly anisotropic lanthanide ions with the goal of identifying features relevant to modulating the spin topology. The synthetic strategy is to design molecules with spin chirality through frustration-perturbation or frustration-induced strategy by introducing competitive coupling and chiral/polar stimuli. The structural topology, local moments, magnetic interactions and chiral/polar effects and their influences to the total spin texture will be probed through combined experimental (spectroscopic, magnetic, high frequency/high field EPR, μSR and INS) and theoretical study. The information extracted from such studies will be without doubts of importance for the rational design of new materials with spin chirality.

自旋阻挫是磁学领域多种多样新奇物性的内在驱动力。打破相互作用自旋之间阻挫的微妙平衡，可以诱发自旋拓扑转变，获得在量子计算、高密度信息存储等方面具有广阔应用前景的自旋手性拓扑结构。本项目拟通过耦合竞争、手性/极性诱导破坏自旋阻挫体系的作用平衡，诱发自旋结构向自旋手性拓扑转变，通过详尽的结构、手性、磁性表征并结合先进的实验方法（如高频/高场EPR、μSR、非弹性中子散射等）和ab initio理论计算揭示自旋手性与配合物自旋中心的空间排布方式、局域磁矩特性、耦合竞争以及外部诱导之间的关系，阐明自旋手性的构筑机理，建立利用自旋阻挫拓展新功能、设计新材料的方法，为先进分子磁性材料的开发提供指导。

具有特殊自旋拓扑的环形磁矩在量子计算、高密度信息存储及作为多铁材料等方面具有广阔应用前景。然而环形磁矩的设计与调控是化学与材料研究领域中具有挑战性的课题。为此，项目从阻挫入手，设计了系列结构独特的稀土配合物，通过精心调控和详尽的磁性表征并结合理论计算，系统研究了自旋中心的配位环境及空间结构特性对自旋拓扑的影响和诱导调控机制，构筑了首例四面体Dy4单分子磁环，组装了结构独特的环形螺旋及Dy6螺旋单分子磁环。通过结构修饰，利用还原及二聚多齿席夫碱配体构筑了四边形Tb4单分子磁环，调控了环形磁矩性质。在赤道位置引入氟原子，有效弱化横向晶体场，设计了室温稳定的高性能手性稀土单分子磁体，创造了新的能垒记录，利用“手性诱导联合对称性破缺”策略构筑了空气稳定高性能极性稀土单分子磁体，实现了自旋拓扑调控和高性能稀土单分子磁体合理设计，为进一步开展磁电耦合功能材料研究打下坚实基础。