Functional Complex Palladium Oxides

非技术摘要：磁性氧化物化合物通常是从元素周期表的第四行提取的磁性组分，也被称为第一过渡系列。人们通常与磁铁联系在一起的元素，如铁，通常也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，开发含有不属于第一过渡系列的元素的新型磁性材料可能是非常有回报的。在材料研究部固态和材料化学计划的支持下，这一具体项目侧重于第二个跃迁系列中的一个成员--元素钯。尽管由于许多技术原因，制造钯的磁性氧化物具有很高的挑战性，但无论是从基础科学的角度还是从新的应用来看，结果都可能非常有趣。这些新材料表现出的磁性本质改变了目前人们对磁性行为的许多看法，并为磁性技术开辟了新的方向。这些包括在磁数据存储方面的应用，磁开关的新方法，以及用于高效电机和风力涡轮机的新一代磁铁。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复杂氧化物：这类材料能否从已知的少数几个罕见的例子显著扩大。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，并分别实现非金属到金属过渡过程中钯化合物的成分调整。要实现上述目标，需要克服两大挑战，一是钯的憎氧性质，二是钯离子采用与8d电子有关的抗磁性正方形平面构型的强烈倾向。第一个问题就是制备和稳定含二价钯的氧化物的难度。事实上，在这个方向上的任何努力都会增加相对较少的库存。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，这将导致不成对的自旋。对于稳定氧化物中钯离子的挑战，提出的解决方案包括了解和利用正电离子的诱导效应来扩大已知的复杂钯氧化物的数量。阳离子“软化”氧，生成稳定的钯氧化物，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主体结构和板模型，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Pd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，并将提供4d磁性信息。绝缘4D磁体具有比3D磁体更高的有序化温度，在作为具有较高磁有序化温度的新型磁介质材料方面具有广阔的应用前景。

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.