Rational design and quantum chemistry of complex itinerant intermetallic magnets: syntheses, crystal structures, magnetic properties and quantum-chemical calculations of new complex borides of the transition metals, M9M`2T18-xT`xB8 (M = Sc, Ti; M` = Mn, F

本项目将实验和理论结合起来，设计制备和随后的表征，并深入了解新的金属间铁磁体和反铁磁体。主要概念包括使用一个复杂的金属硼化物框架与磁性三维元素，例如，Cr, Mn, Fe， Co和Ni，插入到具有低维特征的磁性结构的空隙中。这些材料将通过x射线和中子衍射以及磁化实验来研究，以确定原子和磁性结构。在这些结构的各种模型上的电子结构的理论确定将为进一步的原子取代合成工作提供反馈，以创造具有目标磁性的新化合物。这一努力代表了针对新型磁性材料的实验和理论的强大协同耦合，并可能导致由于磁性交换的潜在一维特征而具有不寻常的体磁性的新材料。新合成的化合物Ti9Fe2Ru18B8将会成为一种坚固、复杂结构的潜在衍生物。新的金属间化合物系列M9M¿2T18-xT¿xB8 （M和T代表金属元素；M¿特别表示磁性金属元素）将作为一个化学系统，其中价电子的数量可以调整，以诱导所需的磁性。温度相关结构分析、中子衍射实验、磁测量和量热法将对这些产品进行表征。理论研究将从更简单的四边形体系M2M¿T5-xT¿xB2开始，其中价电子的数量从61到67个电子变化，并显示出局部磁行为的变化，然后进化到更复杂的系统。该项目是亚琛工业大学无机化学研究所的固态化学小组和爱荷华州立大学化学系之间的密切合作。亚琛小组将扩展其现有的合成经验，使用经典的高温合成路线合成这种新系列的几种化合物，使用衍射方法和EDX分析来表征它们，并测量它们的磁性能。与这些合成工作并行，ISU小组将使用电子结构封装和化学键分析来了解这些复杂相的电子和磁性行为，并预测亚琛小组的新合成目标。此外，ISU小组将进行温度依赖的单晶研究，以探索结构变化与磁性行为的细节。对于任何铁磁产品，也将进行量热测量来探索它们的磁热效应，这对于阐明可能的热磁应用是重要的。同样，两个小组将通过实验（中子衍射）和理论（自旋极化超级单体计算）的努力来澄清新化合物的自旋结构。

This project combines experiment and theory towards the designed preparation and subsequent characterization and thorough understanding of new intermetallic ferromagnets and antiferromagnets. The primary concept involves using a complex metal boride framework with magnetic 3d elements, e.g., Cr, Mn, Fe, Co and Ni, inserted in voits that create magnetic structures with low-dimensional character. These materials will be studied by X-ray and neutron diffraction as well as magnetization experiments to determine atomic and magnetic structures. Theoretical determination of the electronic structures on various models of these structures will provide feedback toward further synthetic efforts of atomic substitutions to create new compounds with targeted magnetic behavior. This effort represents a strong, synergistic coupling of experiment and theory that targets new magnetic materials, and may lead to new materials with unusual bulk magnetic properties due to the potential one-dimensional character of the magnetic exchange. Experimental effort will initiate with potential derivatives of a robust, complex structure type, as found for the newly synthesized compound Ti9Fe2Ru18B8. The new intermetallic series M9M¿2T18-xT¿xB8 (M and T represent metal elements; M¿ specifically indicates a magnetic metal element) will serve as a chemical system in which the numberof valence electrons can be tuned to induce desired magnetic properties. Temperature-dependent structure analyses, neutron diffraction experiments, magnetic measurements and calorimetry will be carried out to characterize these products. Theoretical investigations will start with the simpler tetragonal system, M2M¿T5-xT¿xB2, in which the number of valence electrons varies from 61 to 67 electrons and shows variation in local magnetic behavior, and then evolve to the more complex systems.This project is a close collaboration between solid-state chemistry groups at the Institute of Inorganic Chemistry at RWTH Aachen and the Chemistry Department at Iowa State University (ISU). The Aachen group will extend its present synthetic experience using classical high temperature synthetic routes to synthesize several compounds in this new series, characterize them using diffraction methods and EDX analyses and measure their magnetic properties. Parallel to these synthetic efforts, the ISU group will use electronic structure packages and chemical bonding analyses to understand the electronic and magnetic behavior of these complex phases and predict new synthetic targets for the Aachen group. In addition, the ISU group will carry out temperature-dependent single crystal studies to explore details in structural changes with magnetic behavior. For any ferromagnetic products, calorimetric measurements will also be conducted to explore their magnetocaloric effects, which is important for elucidating possible thermomagnetic applications. Likewise, both groups will clarify the spin structures of the new compounds by experimental (neutron diffraction) and theoretical (spin-polarized supercell calculations) efforts.