Materials World Network: Designed preparation, characterization, magnetic properties and quantum chemical calculations of new complex itinerant magnets, Ti8-xM3+xRu18-yRhyB8 (M = Cr,Mn, Fe, Co, Ni; 0 less than x less than 2; 0 less than y less than 18)

本项目将理论与实验相结合，对新型复杂过渡金属硼化物的制备、表征和理论研究，这些硼化物是潜在的磁体，即铁磁体、铁磁体或反铁磁体。具有磁性活性的三维金属占据复杂金属硼化物框架的空隙，导致这些磁性金属的低维结构，从而导致低维磁性行为。实验工作将集中在新的金属间化合物系列Ti8-xM3 + xRu18-yRhyB8 （M = Cr, Mn, Fe, Co, Ni; 0≤x≤2;0≤y≤18）上，其中价电子的数量可以通过Ru:Rh的比值来改变。由于价电子的数量可以调整，我们期望在这些相中诱导所需的磁性，特别关注实现巡回铁磁性，这是一种罕见的磁性，尚未在其他复杂的硼化物中观察到。将对新化合物进行结构表征，并确定其磁性能。结合实验成果，对这些结构的各种模型的电子结构和原子间磁（交换）耦合的理论确定将为进一步合成具有目标磁性质的新相提供反馈。此外，理论工作将建立化学键因子和局部交换相互作用之间的关系，这些相互作用决定了这些情况下和其他流动磁铁的磁性结构。因此，这项活动的智力价值在于理解金属间化合物的化学成分和磁性行为之间的关系，这将通过实验和理论的协同参与来完成。这项工作的广泛影响包括为合成化学家寻找具有理想磁性的新型流动磁铁建立规则，以及确定铁磁性、铁磁性和反铁磁性的化学和物理标志。该项目是亚琛工业大学无机化学研究所固态化学小组和爱荷华州立大学化学系之间的密切合作。亚琛小组将扩展其目前的合成经验，使用高温方法合成这种新系列的几种化合物。此外，他们将使用衍射方法和EDX分析来表征它们，并测量它们的磁性能。同时，ISU小组将使用电子结构封装，化学键分析和多重散射理论来了解合成相的磁性行为，并预测亚琛基团的新合成目标。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，也将进行量热测量以探索其潜在的磁热效应，这对于阐明可能的热磁应用非常重要。同样，这两个小组将通过实验（中子衍射）和理论（自旋极化超级细胞计算）的努力来澄清新化合物的自旋结构。在这个项目中，凝聚态系统的实验和理论的结合为研究生提供了一个真正的跨学科问题-他们将清楚地了解不同的科学主题和模型如何影响其他领域。本项目在德国亚琛和爱荷华州艾姆斯的研究生将有机会进行交流，他们将学习固态化学研究的实验和理论组成部分。

This project combines theory and experiment towards the preparation, characterization and theoretical study of new complex transition metal borides which are potential magnets, i.e., ferromagnets, ferrimagnets or antiferromagnets. Magnetically active 3d metals occupying voids in complex metal boride frameworks give rise to low-dimensional structures of these magnetic metals, which may result in low-dimensional magnetic behavior. Experimental efforts will focus on the new intermetallic series, Ti8–xM3+xRu18–yRhyB8 (M = Cr, Mn, Fe, Co, Ni; 0 ≤ x ≤ 2; 0 ≤ y ≤18), in which the number of valence electrons can be varied by the Ru:Rh ratio. Since the number of valence electrons can be tuned, we anticipate inducing desired magnetic properties in these phases, with a particular focus on achieving itinerant ferrimagnetism, which is a rare magnetic property not yet observed in other complex borides. The new compounds will be structurally characterized, and their magnetic properties will be determined. Together with the experimental effort, theoretical determination of the electronic structures and interatomic magnetic (exchange) couplings for various models of these structures will provide feedback toward further synthetic efforts of new phases with targeted magnetic properties. Furthermore, theoretical work will establish a relationship between chemical bonding factors and local exchange interactions that dictate the magnetic structure in these cases and other itinerant magnets. Thus, the intellectural merit of this activity is to understand the relationship between chemical composition and magnetic behavior in intermetallic compounds, which will be accomplished through a synergistic engagement of experiment and theory. The broader impacts of the effort include establishing rules for synthetic chemists to search for new itinerant magnets with desired magnetic properties, as well as to identify chemical and physical signposts for ferromagnetism, ferrimagnetism and antiferromagnetism.This project is a close collaboration between solid-state chemistry groups at the Institute of Inorganic Chemistry at RWTH Aachen University and the Chemistry Department at Iowa State University (ISU). The Aachen group will extend its present synthetic experience using high-temperature methods to synthesize several compounds in this new series.Furthermore, they will characterize them using diffraction methods and EDX analyses, and measure their magnetic properties. Concurrently, the ISU group will use electronic structure packages, chemical bonding analyses and multiple scattering theories to understand the magnetic behavior of the synthesized 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 potential 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 super-cell calculations) efforts.The combination of experiment and theory for condensed matter systems in this project provides graduate students a truly interdisciplinary problem – they will clearly learn how different scientific subjects and models impact other areas. The graduate students in this project in Aachen, Germany and Ames, Iowa will have opportunities for exchange, and they will learn both experimental and theoretical components of research in solid-state chemistry.