Materials World Network: Targeting New Complex Itinerant Magnets Using Experiment and Theory

该材料世界网络项目由固态和材料化学计划以及材料研究部特别计划办公室支持，将合成，衍射，磁化测量与第一原理电子结构理论相结合，以设计和理解新的金属间铁磁体和反铁磁体。 实验活动将集中在具有磁性3d元素的复杂4d和5d金属硼化物框架上，例如，Cr-Ni，插入空隙中以产生具有低维特征的磁性结构。金属-硼化物框架结构坚固、电子稳定，并且提供了通过传导电子上的自旋在相邻磁性金属原子之间进行磁性交换的机制。 以前的支持集中在四重对称的结构上;新的发现将我们的研究扩展到六重和三重对称，其中挫折效应可以影响磁性行为。 具体而言，原子和磁性结构将通过X射线和中子衍射以及磁化实验来确定。 电子结构理论将通过评估轨道和交换相互作用来探索各种原子和磁性结构的能量学，以建立化学规则并计算铁磁或反铁磁行为的转变温度。 理论结果将为后续的合成目标提供反馈与预测的磁性行为。 理论还将研究更简单的MM 'P和MM'As（M，M' = V-Cu）的磁结构和特性，它们也显示出四方和三方对称性。 这项工作将确立理论方法的普遍性。 目前，对于具有永磁行为的目标化合物，还没有通用的化学规则。 成功的结果将建立一个单一的结构家族内的磁行为的演变，以确定磁行为的趋势，作为各种化学和物理参数的变化，以系统的方式。 非技术总结这项科学工作结合了实验和理论，设计和制备了属于最近发现的富金属化合物家族的新磁体。 这些化合物的复杂性允许化学调整，这可以通过合成来实现，并且可以通过量子化学来研究。 通过对化合物化学家族的系统研究，将出现一套针对金属永磁体的新规则，这些规则具有许多技术应用。 真实的挑战将是通过理论预测这种目标材料将显示永磁行为的温度范围。 科学的努力将为学生提供一个真正的跨学科的问题，通过结合化学和物理实验和理论。 学生参与者将清楚地了解不同的科学科目和方法如何影响其他科学领域。 来自德国亚琛和爱荷华州艾姆斯的学生将有机会交流，他们将学习固态化学研究的实验和理论部分。 总之，这项工作代表了实验和理论的强大协同耦合，将识别和表征新的磁性材料，更广泛的目标是建立用于构建新磁体的预测规则。

TECHNICAL SUMMARYThis Materials World Network project,supported by the Solid-State and Materials Chemistry program and the Office of Special Programs in the Division of Materials Research, combines synthesis, diffraction, magnetization measurements with first principles electronic structure theory to design and understand new intermetallic ferromagnets and antiferromagnets. Experimental activity will focus on complex 4d and 5d metal-boride frameworks with magnetic 3d elements, e.g., Cr-Ni, inserted in voids to create magnetic structures with low-dimensional character. The metal-boride framework is a structurally strong, electronically robust, and provides a mechanism for magnetic exchange between adjacent magnetic metal atoms via the spins on the conduction electrons. Previous support focused on structures with four-fold symmetry; new discoveries expand our studies to six-fold and three-fold symmetry, in which frustration effects can influence magnetic behavior. Specifically, atomic and magnetic structures will be determined by X-ray and neutron diffraction as well as magnetization experiments. Electronic structure theory will probe the energetics of various atomic and magnetic structures by evaluating orbital and exchange interactions to establish chemical rules and to calculate transition temperatures for ferromagnetic or antiferromagnetic behavior. Theoretical results will provide feedback for subsequent synthetic targets with predicted magnetic behavior. Theory will also investigate the magnetic structures and characteristics of the simpler MM'P and MM'As (M, M' = V-Cu), which also show tetragonal and trigonal symmetries. This work will establish the generality of the theoretical approach. At present, no general chemical rules exist to target compounds with permanent magnetic behaviour. The successful outcome will establish the evolution of magnetic behavior within a single structural family to identify trends in magnetic behavior as various chemical and physical parameters change in systematic ways. NON-TECHNICAL SUMMARYThis scientific effort combines experiment and theory to design and prepare new magnets belonging to a recently discovered family of metal-rich compounds. The complexity of these compounds allows chemical tuning, that can be accomplished by synthesis and can be studied by quantum chemistry. From this systematic study of a chemical family of compounds, a new set of rules will emerge for targeting metallic, permanent magnets, which have numerous technological applications. The real challenge will be to predict, via theory, the temperature range at which such targeted materials will show permanent magnetic behavior. The scientific effort will provide students a truly interdisciplinary problem, by combining chemistry and physics with experiment and theory. The student participants will clearly learn how different scientific subjects and approaches impact other scientific areas. The student participants from 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. In summary, this effort represents a strong, synergistic coupling of experiment and theory that will identify and characterize new magnetic materials, with the broader goal of establishing predictive rules for building newer magnets.