Fabrication and Characterization of Multilayer Nanostructures of Manganites

9707687 Li这项研究计划资助金旨在解决三层隧道结和多层锰氧化物纳米结构的合成和加工问题。根据磁阻效应的结果，由于这些材料中的自旋极化程度很高，因此在这些材料中可能会有很大的自旋极化隧道效应。该方法是利用人工制造的三层结和多层结构作为具有可控结参数的定制系统来系统地研究这种现象。规划期间的目标是研究利用宾夕法尼亚州立大学的国家纳米制造设施制造和表征小面积多层隧道接头的可行性。主要的研究领域是：1)人工三层结结构的外延生长，该结构由两个由薄的绝缘层隔开的锰氧化物层组成，界面尖锐，漏电低。将测试不同的绝缘层，并表征结的结构和界面性质；2)将结刻画成小尺寸的图案，目的是在两个锰层中实现单一的磁畴，每层的磁矩反平行；3)研究不同结尺寸、锰层厚度、阻挡层材料和厚度的结的自旋相关的磁输运和磁性能。预计该项目的可行性将被确定，随后将系统地研究锰氧化物中的自旋极化隧穿效应，它们与样品结构和参数的关系，以及与理论模型的比较。该项目解决了材料科学中与电子技术相关的一个热门领域的基础研究问题。这些研究对于更好地理解自旋极化输运，特别是锰氧化物薄膜和多晶样品中的反常磁阻效应具有重要意义。同时，目前的研究也解决了与技术直接相关的问题，因此直接影响到巨磁电阻材料的潜在应用。***

9707687 Li This Research Planning Grant(RPG) addresses synthesis and processing issues in the fabrication of trilayer tunnel junctions and multilayer nanostructures of manganites. Based on results of magnetoresistance effects, a large spin-polarized tunneling effect is expected in manganites because of the large degree of spin polarization in these materials. The approach is to use artificially fabricated trilayer junctions and multilayer structures as tailored systems with controlled junction parameters to systematically study the phenomena. The objective during the planning period is to study the feasibility of fabricating and characterizing small-area multilayer tunnel junctions using the National Nanofabrication Facilities at Penn State. Principal research areas to be pursued are: 1) epitaxial growth of artificial trilayer junction structures consisting of two manganite layers separated by a thin insulating barrier layer with sharp interfaces and low leakage. Different insulator layers will be tested and the structural and interfacial properties of the junction will be characterized; 2) lithographically pattern the junction into small with the goal of achieving single magnetic domain in both manganite layers with the magnetic moment in each layers antiparallel; 3) study spin-dependent magneto-transport and magnetic properties of the junctions with different junction sizes, manganite layer thicknesses, and barrier layer materials and thicknesses. It is anticipated that the feasibility of the project will be ascertained, and a systematic study on the effect of spin-polarized tunneling in manganites, their relation with sample structures and parameters, and a comparison with theoretical models will follow. %%% The project addresses basic research issues in a topical area of materials science having technological relevance to electronics. These studies are important for greater understanding of spin-polarized transport in general, and the anomalous magnetoresistance effects in manganite thin films and polycrystalline samples in particular. At the same time, the current research also addresses issues directly related to the technologies and therefore has direct impact on the potential application of the colossal magnetoresistance materials. ***