非局域电子态诱导磁性的内在机理研究

The room-temperature magnetism explored by the experiments in semiconductors and insulators without partially occupied d/f orbitals has attracted extensive research interest. Theoretical researches have predicted that cationic vacancies are the possible origin of the magnetism, which induce localized 2p orbitals. However, the dominant defects in such semiconductors and insulators are anionic vacancies, which will quench the formation of localized 2p electronic states induced by cationic vacancies. Therefore, it is necessary to search for a new origin to understand the observed magnetism. In this proposal, we will study the possibility of anionic vacancies as the origin of the magnetism through density functional calculations. by investigating the non-magnetic materials with different components/electronic properties, we will discuss the possibility of local magnetic moments formed by the delocalized electronic states, and explore the effects of quantum confinement. Moreover, we will carefully study the spin interactions among local magnetic moments, and explore the possible factors to enhance the spin interactions. In addition, we will discuss possible ways to produce high-temperature magnetism. By addressing the aforementioned issues, we will try to find the intrinsic mechanism and the general physical pictures, and predict the possible ways for experimental studies.

在不包含未占满d/f轨道电子的半导体和绝缘体材料中,实验发现的室温磁性吸引了凝聚态物理学界广泛关注。为解释其机理，理论研究预言阳离子缺陷诱导部分占据2p局域化轨道是这种新型磁性的物理起源。但是，样品中占主导地位的是阴离子缺陷,它会淬灭氧离子缺陷诱导的局域化 2p 轨道。因此，理论提出的磁性来源与实验观察到的磁性有显著差异，有必要对实验观察到的磁性机理做进一步探讨。本项目拟采用密度泛函理论方法，研究在不包含未占满d/f轨道电子的半导体和绝缘体中，阴离子缺陷是否可能是磁性的来源，及其形成磁性的内在物理机制。探讨阴离子缺陷产生的非局域电子态转变为局域磁矩的可能性，揭示对非局域电子态进行调控的内在机制。在此基础上，研究非局域电子态形成局域磁矩间的自旋相互作用，探讨形成宏观磁性的可能性和发展方向，得到一般物理规律，为进一步的实验研究提供理论依据和指导。

磁性材料一直是科研人员所关心的重要课题之一。本项目主要研究目标是探索非局域电子态实现磁性的机制，通过研究不同体系、不同性质的非局域电子态，分析其诱导磁性的可行性，讨论其潜在的物理图像。在项目的资助下，基于第一性原理的密度泛函理论计算，开展了下面几个方面的研究：(1) 非局域电子在半导体中诱导磁性的机制及磁性强度研究；(2) 半导体中边界非局域电子态的研究；(3) 层状半导体中非局域电子态的研究。通过相关研究，项目在非局域电子态的研究中取得了一定成果，厘清了非局域电子态和磁性的关联，掌握了磁性诱导的机制。此外，在项目对非局域电子态的研究中，也掌握了非局域电子态对拓扑性质、迁移率等其它性质的影响机制，为进一步发展非局域电子态的研究提供了足够的理论依据。相关研究成果已经在Nano Letter, Phys Rev B, J Phys Chem Lett等国外SCI期刊发表论文16篇。目前仍有多篇受资助论文在国际SCI期刊审稿。