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)

本课题采用理论与实验相结合的方法，对新型铁磁体、亚铁磁体或反铁磁体等新型复合过渡金属硼化物的制备、表征及理论研究进行了研究。在复杂的金属硼化物骨架中占据空位的磁活性3D金属导致了这些磁性金属的低维结构，这可能导致低维磁性行为。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)，其中的价电子数可以通过Ru：Rh的比例来改变。由于价电子的数量可以调节，我们预计在这些相中诱导所需的磁性，特别是实现巡回亚铁磁性，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，并确定它们的磁性。与实验工作一起，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的新相提供反馈。此外，理论工作将建立化学键因素和局部交换作用之间的关系，在这些情况下，局部交换作用决定了这些情况下的磁结构和其他巡回磁体。因此，这项活动的智力价值是理解金属间化合物中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作用来实现。这项工作的更广泛影响包括为合成化学家建立规则，以寻找具有所需磁性的新的巡回磁体，以及确定铁磁性、亚铁磁性和反铁磁性的化学和物理标志。该项目是RWTH亚琛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(ISU)之间的密切合作。亚琛集团将扩展其现有的合成经验，使用高温方法合成这一新系列的几个化合物。此外，他们将使用衍射法和EDX分析对它们进行表征，并测量它们的磁性。同时，ISU小组将使用电子结构包、化学键分析和多重散射理论来了解合成相的磁性行为，并为亚琛小组预测新的合成目标。此外，ISU小组将进行随温度变化的单晶研究，以探索结构随磁性行为变化的细节。对于任何铁磁产品，还将进行量热测量，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，两个小组将通过实验(中子衍射)和理论(自旋极化超晶胞计算)的努力来阐明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学科和模型如何影响其他领域。参加这个项目的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.