Functional Complex Palladium Oxides

非技术文摘：磁性氧化物化合物通常是由从元素周期表的第四行提取的磁性成分制成的，也被称为第一跃迁系列。人们通常与磁铁联系在一起的元素，如铁，也经常是有用的磁性氧化物的主要成分。近年来，越来越多的人认识到，开发含有非第一个过渡系列元素的新型磁性材料可能是非常有益的。在材料研究部固态和材料化学项目的支持下，这个具体的项目集中在第二个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，但从基础科学的角度和新的应用角度来看，结果都非常有趣。这些新材料所显示的磁性性质改变了许多目前对磁性行为的看法，并为磁性技术开辟了新的方向。这些应用包括磁数据存储，磁开关的新方法，以及用于高效电动机和风力涡轮机的新一代磁铁。技术摘要：本项目解决的问题是关于含二价钯离子的功能复合物氧化物化合物：从已知的少数、罕见的例子来看，这类材料能否得到显著扩展？该项目的目标是开发更多的钯的磁性和磁介质氧化物化合物的例子，并分别实现钯化合物在非金属到金属过渡中的成分调谐。为了实现既定的目标，需要克服两个主要的挑战，即钯的疏氧性质和钯离子采用与8 d电子相关的抗磁性方形平面结构的强烈倾向。首先是制备和稳定含二价钯氧化物的困难。事实上，在这个方向上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多面体配位，从而导致不成对的自旋。对于稳定氧化物中钯离子的挑战，提出的解决方案包括理解和利用正电阳离子的感应效应来扩大已知络合钯氧化物的数量。电正离子“软化”氧，并产生稳定的钯氧化物，具有显著的共价钯氧相互作用。该项目采用的方法将包括对整体结构和板模型使用第一性原理计算，与实验工作同时进行，以帮助理解这种感应稳定。微波加热技术的使用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钯金属。该活动将扩大领域，并加强对功能钯氧化物的材料化学和物理的理解，并将为4d磁学提供信息。绝缘4d磁体具有比3d磁体更高的有序温度，并且有望应用于具有相对较高磁有序温度的新型磁介电材料。

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.