New Magnetoresistant Oxides of Mixed 3d/4d/5d Transition Metals

这项提议的目的是研究一种新的混合氧化物系列，主要包含4d和5d过渡金属阳离子，以及来自3D过渡金属系列的额外磁性杂质。我们最近对掺Fe~(3+)的SrRuO_3、CaRuO_3和Sr_2RuO_4的研究揭示了在任何Ruthenate中都不存在的非常大的磁电阻。更广泛地说，这些结果表明，导电氧化物中可能会出现大的局部力矩，这种材料可以被利用来获得新的功能和对陶瓷的新理解。我们的策略是使用强磁性的3D杂质来极化宿主的4d/5d窄导带，从而诱导出大的电学和磁学响应。通过扭曲晶体结构和改变成分，3d杂质的磁态和能量将被系统地改变，以与宿主4d/5d金属的导带相匹配。阳离子有序也将被用作一种工具来引导从自旋受阻的晶内磁阻行为到亚铁磁性的晶间磁阻行为的交叉。我们将对单晶、外延薄膜和多晶进行比较，以确定晶界效应的作用，同时将对有序混合金属氧化物模型进行第一性原理计算，以确定不同阳离子d轨道的电子能级。同时，将利用同步辐射来确定这些化合物的结构和电子态。我们的教育计划将为本科生和高中教师提供培训，为他们提供实验室和研究经验。通过与一家初创公司的合作、协同和探索性研究，将进一步扩展到行业。陶瓷磁体通常是绝缘体。该项目将探索在磁场作用下成为更好导体的新型磁性陶瓷。这些材料过去从未被研究过，但由于自旋电子器件的前景而变得有趣起来。与传统的电子设备相比，自旋电子设备不仅可以检测和传输电子的电荷，还可以检测和传输电子的自旋，从而处理更多的信息。

The objective of this proposal is to investigate a new series of mixed oxides containing primarily 4d and 5d transition metal cations, with additional magnetic impurities from the 3d transition-metal series. Our recent work on Fe3+-doped SrRuO3, CaRuO3, and Sr2RuO4 has revealed a very large magnetoresistance that was not previously known to exist in any ruthenate. More broadly, these results suggest that large local moments can arise in conducting oxides, and such materials can be exploited to gain new functionality and new understanding of ceramics. Our strategy is to use strongly magnetic 3d impurities to polarize the narrow 4d/5d conduction bands of the host, so that large electronic and magnetic responses are induced. The magnetic states and the energies of the 3d impurities will be systematically varied, by distorting the crystal structure and changing the composition, to match with those of the conduction bands of the host 4d/5d metals. Cation ordering will also be used as a tool to direct the crossover from spin-frustrated, intragrain magnetoresistance behavior to ferrimagnetic, intergrain magnetoresistance behavior. Single crystals, epitaxial thin films and polycrystals will be compared to determine the role of the grain-boundary effect, while first-principles calculations of model, ordered mixed-metal oxides will be made to benchmark the electronic energy levels of disparate cation d-orbitals. Meanwhile, synchrotron radiation will be utilized to determine the structures and electronic states of these compounds. Our educational program will offer training to undergraduates and high school teachers to provide them with laboratory and research experience. Further outreach to industry will be made through collaborative, synergistic, and exploratory research with a start-up company.Ceramic magnets are typically insulators. This project will explore new magnetic ceramics that become better conductors under a magnetic field. These materials have not been studied in the past but are becoming interesting because of the prospect of spintronic devices. Compared to conventional electronic devices, spintronic devices process more information by detecting and transmitting not only the charge but also the spin of electrons.