基于μ子自旋技术的双自由基分子材料电子结构与自旋动力学的研究

Di-radical (DR) molecules have shown their unique electrical properties in response to magnetic field, due to their unique electronic spin structures, thus have become one of the potential candidates in organic spintronics. The DR materials could achieve an excited-state triplet in equilibrium with the ground state, which is critical to achieve room temperature high-performance spintronics devices, due to the fact that the high spin-state triplet can be thermally activated at room temperature. To fundamentally understand the microscopic electronic spin structures of the DR and the dynamical process of the triplet relaxation, is the necessary prerequisite to optimising and designing the organic spintronics devices. However, the current conventional techniques may have difficulty in tackling the highly de-localised system to achieve a better hyperfine structure, so that the investigation experimentally into microscopic spin structures has been limitted. Based on our previous successful experience on using muon spin techniques to investigate the electronics structure of the close-shell organic molecule, we propose to use the same experimental method to study the electronic structure and spin dynamics of DR molecular materials, by making use of the high density of the diradical system, as well as muon's high sensitivity to the spin system. This work can provide useful complementary information to the microscopic studies by conventional magnetic resonance techniques, as well as fundamental support for developing a systematic approach to microscopically study radical materials based on muon techniques.

双自由基分子具有特殊的自旋电子结构和灵敏的磁场响应特性，已成为有机自旋电子学领域关注的新型材料，其在室温下可稳定获得大量的三线态，对大幅提升室温工作的有机自旋电子器件性能起着关键性作用。深入认识和理解双自由基的微观自旋结构及三线态动力学弛豫过程是优化设计有机自旋电子材料及器件的先决条件。但目前由于传统相关技术在探测高度离域的系统上常常无法分辨较为精细的结构，导致实验方面，对双自由基分子微观自旋结构的研究，尚显不足。因此，基于申请人以往运用μ子自旋技术探测有机分子光致三线态电子结构方面的成功经验，本项目提出，充分利用双自由基丰富的自旋密度、及μ子对自旋电子体系极为敏感的独特优势，使用μ子自旋技术来探测和解析双自由基分子材料电子结构与自旋动力学过程，以补充目前高度离域化的双自由基分子材料微观探测的空白，也为建立一个基于μ子自旋技术的系统地研究自由基分子材料的微观探测方法提供重要工作基础。

特殊的自旋电子结构使得双自由基分子在室温下可稳定获得大量的高自旋态，对大幅提升室温工作的有机自旋电子器件性能起着关键作用。深入认识和理解双自由基的微观自旋态及其动力学弛豫过程是选择有机自旋电子材料的先决条件。但目前传统自旋共振技术在探测高度离域化的材料上常常无法分辨其精细结构。为弥补实验探测自由基材料的空白，本项目充分利用微观“磁针”μ子对局域自旋极为敏感的独特优势，首次使用μ子自旋共振技术来测量自由基分子的自旋微观结构在基态和激发态之间的差异。本项目首次实现了对自由基分子自旋结构的定位解析，测到了高自旋密度的自由基中心在分子中的转移，并通过实验对比和理论分析深入研究了自由基的微观自旋弛豫机制，为建立μ子自旋技术的系统性研究自由基分子材料提供了重要工作基础。