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

本提案的目的是研究一系列新的混合氧化物，主要含有4D和5D过渡金属阳离子，并含有来自3D过渡金属系列的额外磁性杂质。我们最近对Fe 3+掺杂的SrRuO 3、CaRuO 3和Sr 2 RuO 4的研究揭示了之前未知的任何钌酸盐中存在的非常大的磁电阻。更广泛地说，这些结果表明，大的局部力矩可以出现在导电氧化物，这样的材料可以被利用，以获得新的功能和新的理解陶瓷。我们的策略是使用强磁性的3d杂质来取代主体的窄4d/5d导带，从而诱导出大的电子和磁性响应。通过扭曲晶体结构和改变成分，3d杂质的磁性状态和能量将系统地变化，以与宿主4d/5d金属的导带相匹配。阳离子排序也将被用作一种工具，以指导从自旋受抑，晶内磁阻行为到亚铁磁，晶间磁阻行为的交叉。单晶，外延薄膜和多晶将进行比较，以确定晶界效应的作用，而模型的第一原理计算，有序的混合金属氧化物将基准的不同阳离子d-轨道的电子能级。同时，同步辐射将被用来确定这些化合物的结构和电子状态。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，将进一步拓展到行业。陶瓷磁体通常是绝缘体。该项目将探索在磁场下成为更好导体的新型磁性陶瓷。这些材料在过去没有被研究过，但由于自旋电子器件的前景而变得有趣。与传统的电子器件相比，自旋电子器件通过检测和传输电子的电荷和自旋来处理更多的信息。

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.