Correlated electronic structure, spin interactions, and electron-lattice couplings in mixed-valence lacunar spinels

混合价空穴尖晶石中的相关电子结构、自旋相互作用和电子晶格耦合

• 批准号: 437124857
• 负责人: Dr. Liviu Hozoi
• 金额: --
• 依托单位: Lehrstuhl für Experimentalphysik V
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/437124857?language=en
• 关键词: Correlated; electronic; structure; spin; interactions

Various lacunar-spinel compounds, described by the chemical formula AM4X8, are being intensively investigated in relation to strong magneto-electric couplings, of potential use in novel devices. Their magnetically active structural units are tetrahedral clusters of d-metal ions, arranged in a manner resembling the breathing-pyrochlore crystal structure.So far, density-functional theory (DFT) has been the computational tool to address their electronic structures. It is known and well documented however that state-of-the-art wavefunction-based ab initio computations on similar compounds, e.g., cubane-type ferrodoxin proteins with a Fe4 kernel or tetrahedral Nb4 clusters, indicate for the transition-metal tetrahedra genuine many-body physics that can not be captured by single-configuration DFT: non-Aufbau filling of the single-particle levels, near-degeneracy of a large number of electron configurations, strong configurational mixing. It is then highly desirable to clarify the extent of such many-body effects in AM4X8 lacunar spinels and their role when it comes to the remarkable magnetic properties of these systems. This defines the main goal of this project.We shall employ to this end ab initio many-body techniques as developed in quantum chemistry and the outcome of such computations will be carefully analyzed vis-a-vis experimental investigations, ranging from ESR and NMR measurements to EXAFS and RIXS spectroscopy. Our work will contribute to new insights into the correlated electronic structures and the unique physical properties of the lacunar spinels. The results will also provide useful reference data in the context of related cluster compounds where electronic states in the form of correlated molecular orbitals are spread out over small groups of open-d-shell ions and imply new flavors of many-body effects and very unusual properties, e.g., the breathing pyrochlores or the swedenborgite-type cobaltites.

化学式 AM4X8 描述的各种空穴尖晶石化合物正在深入研究与强磁电耦合相关的问题，这些化合物在新型器件中具有潜在的用途。它们的磁活性结构单元是d-金属离子的四面体簇，排列方式类似于呼吸烧绿石晶体结构。到目前为止，密度泛函理论（DFT）已成为解决其电子结构的计算工具。然而，众所周知且有据可查的是，对类似化合物（例如具有 Fe4 核或四面体 Nb4 簇的立方烷型铁氧还蛋白）进行最先进的基于波函数的从头算，表明过渡金属四面体真正的许多-单构型DFT无法捕获的体物理：单粒子能级的非Aufbau填充、大量电子构型的近简并性、强构型混合。因此，非常需要澄清 AM4X8 空心尖晶石中这种多体效应的程度以及它们在这些系统的显着磁性方面的作用。这定义了该项目的主要目标。为此，我们将采用量子化学中开发的从头开始多体技术，并且将通过 ESR 和 NMR 测量等实验研究仔细分析此类计算的结果EXAFS 和 RIXS 光谱。我们的工作将有助于对空穴尖晶石的相关电子结构和独特物理性质的新见解。研究结果还将在相关簇化合物的背景下提供有用的参考数据，其中相关分子轨道形式的电子态分布在一小群开放d壳离子上，这意味着多体效应的新风味和非常不寻常的性质，例如呼吸烧绿石或瑞典硼镁石型钴矿。