Fabrication and Characterization of Multilayer Nanostructures of Manganites

9707687李本研究计划补助金（RPG）解决三层隧道结和锰氧化物的多层纳米结构的制造中的合成和处理问题。基于磁电阻效应的结果，由于锰氧化物材料中的自旋极化程度很大，因此预期锰氧化物中会有很大的自旋极化隧穿效应。 该方法是使用人工制造的三层结和多层结构作为定制的系统与控制的结参数，系统地研究的现象。计划期间的目标是研究使用宾夕法尼亚州立大学的国家纳米纤维设施制造和表征小面积多层隧道结的可行性。主要研究方向为：1）人工三层结结构的外延生长，该结构由两个锰氧化物层组成，中间由一层薄的绝缘阻挡层隔开，具有尖锐的界面和低泄漏。将测试不同的绝缘体层，并表征结的结构和界面性质; 2）将结光刻图案化为小的，目标是在两个锰氧化物层中实现单磁畴，其中每个层中的磁矩反平行; 3）研究了不同结尺寸、不同锰氧化物层厚度以及阻挡层材料和厚度。预计该项目的可行性将得到确认，并将对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进行系统研究。该项目解决了与电子技术相关的材料科学专题领域的基础研究问题。这些研究对于更好地理解一般的自旋极化输运，特别是锰氧化物薄膜和多晶样品中的异常磁电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，因此直接影响到庞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. ***