Functional Complex Palladium Oxides

磁性氧化物化合物通常由从元素周期表的第四行提取的磁性成分制成，也被称为第一过渡系列。通常与磁铁有关的元素，如铁，也常常是有用的磁性氧化物的主要成分。近年来，人们越来越认识到，开发具有非第一过渡系列元素的新型磁性材料可能非常有益。在材料研究部门的固态和材料化学计划的支持下，该特定项目侧重于第二过渡系列的一个成员，元素钯。虽然由于许多技术原因，制造钯的磁性氧化物极具挑战性，但无论是从基础科学的角度还是新的应用来看，结果都非常有趣。这些新材料显示的磁性性质改变了目前对磁性行为的许多想法，并允许开辟磁性技术的新方向。这些应用包括磁性数据存储、磁性开关的新方法以及用于高效电动机和风力涡轮机的新一代磁体。技术摘要：该项目解决的问题是关于含有二价钯离子的功能性复合氧化物化合物：这类材料能否从已知的少数罕见的例子中显着扩展。该项目的目标是开发更多钯的磁性和磁介电氧化物化合物的例子，并分别实现钯化合物在非金属-金属过渡中的成分调整。需要克服两个主要的挑战，以实现所述的目标，与疏氧性质的钯和钯离子的非常强烈的倾向，采用抗磁性，正方形平面配置与8 d电子。第一个简单的困难是制备和稳定含有二价钯的氧化物。 实际上，这方面的任何努力都将增加相对较小的库存。与制备磁性钯氧化物相关的第二个挑战是诱导二价钯离子采用会导致不成对自旋的多面体配位。针对稳定氧化物中的钯离子的挑战提出的解决方案包括理解和采用正电性阳离子的诱导效应以扩大已知的复合钯氧化物的数量。正电性阳离子“软化”氧，并导致稳定的钯氧化物具有显著的共价钯-氧相互作用。该项目采用的方法将包括使用第一原理计算的散装结构和平板模型，同时进行实验工作，以帮助理解这种感应稳定。使用微波加热技术将有助于在足够低的温度下快速制备新化合物，从而避免自动还原为Pd金属。该活动将扩大领域，并加强对功能性钯氧化物的材料化学和物理的理解，并将告知4d磁性。绝缘4d磁体具有比它们的3d对应物更高的有序温度，并且有希望用于包括具有相对高的磁有序温度的新型磁介电材料的应用。

Non-technical abstract:Magnetic oxide compounds are often made with the magnetic constituent being drawn from the fourth row of the periodic table, from what is also referred to as the first transition series. The elements that one normally associates with magnets, such as iron, are also frequently the chief components of useful magnetic oxides. In recent years, there has been a growing recognition that developing new kinds of magnetic materials with elements that are not from the first transition series can be highly rewarding. With support of the Solid State and Materials Chemistry Program in the Division of Materials Research, this specific project focuses on one member of the second transition series, the element palladium. While making magnetic oxides of palladium is highly challenging for a number of technical reasons, the results can be deeply interesting, both from the fundamental science perspective as well as new applications. The nature of magnetism that these new materials display changes a lot of the current thinking on magnetic behavior, and allows for new directions in magnetic technologies to be opened up. These include applications in magnetic data storage, novel approaches to magnetic switching, and new generations of magnets for high-efficiency electric motors and wind turbines. Technical abstract:The problem addressed in the project is in regard to functional complex oxide compounds containing divalent palladium ions: Can this class of materials be significantly expanded, from the few, rare example that are known. The goals of the project are to develop more examples of magnetic and magnetodielectric oxide compounds of palladium, and separately, achieve compositional tuning of palladium compounds across non-metal-to-metal transitions. Two major challenges need to be overcome to achieve the stated goals, associated with the oxophobic nature of palladium and the very strong tendency of palladium ions to adopt the diamagnetic, square-planar configuration associated with 8 d electrons. The first is simply the difficulty of preparing and stabilizing oxides containing divalent palladium. Indeed, any effort in this direction would add to a comparatively small inventory. The second challenge associated with preparing magnetic palladium oxides is to induce divalent palladium ions to adopt the kinds of polyhedral coordination that would result in unpaired spins. The proposed solutions to the challenge of stabilizing palladium ions in oxides include understanding and employing inductive effects of electropositive cations to expand the number of known complex palladium oxides. Electropositive cations "soften" oxygen, and result in stable palladium oxides with significantly covalent palladium-to-oxygen interactions. The methods employed for the project will include the use of first-principles calculations on bulk structures and slab models, carried out concurrently with experimental efforts, to aid in understanding such inductive stabilization. The use of microwave heating techniques will aid in the rapid preparation of new compounds at low enough temperatures that auto-reduction to Pd metal is avoided. The activity will expand the domain, and enhance understanding of the materials chemistry and physics of functional palladium oxides, and will inform 4d magnetism. Insulating 4d magnets have higher ordering temperatures than their 3d counterparts and are promising for applications including as novel magnetodielectric materials with relatively high magnetic ordering temperatures.