Investigation of Depth-Dependence in Strongly Correlated Magnetic Oxides by Integrated Experiments and Theory

非技术摘要：材料的表面具有不同于本体的性质。可以操纵、消除或增强这种差异，以改善所需的性能并创造更好、更有用的装置。 这项工作的重点是一类磁性薄膜，希望提供广泛的未来应用在计算，电子，甚至发电。理论和实验的强有力合作将有利于计划工作的质量，提供一种方法来从理论上描述观测结果，并建立观测到的材料特性随深度变化的模型。该项目将支持博士生在先进的真空沉积和理论和表征技术的教育;一个行之有效的方法，提供良好的培训机会，从而在学术和技术环境中的生产性科学事业。从这些研究中预期增加的物理理解的磁性和薄膜中的界面特性将特别相关的技术应用，包括薄磁性薄膜，如磁记录，自旋产生，自旋操纵和/或自旋检测。对表面和界面性质的更深入理解将使更小的设备使用更少的材料，更高的能源效率和更快的通信。技术摘要：表面和界面的磁性和其他性质通常与体不同，这可能对依赖这些性质的技术产生重大影响。为了开发增强的界面和潜在的新界面现象，强烈的竞争是有利的。强关联氧化物，与他们之间的竞争的电荷，自旋和轨道自由度提供了许多有前途的系统，可以允许这些可调参数。该项目将研究强相关磁性LaxSr 1-xMnO 3（LSMO）薄膜，该薄膜已被广泛用于隧道结和固体氧化物燃料电池等应用。使用扫描透射电子显微镜和新开发的深度依赖性X射线吸收分析模型的磁化强度和其他属性与深度，这些参数的偏差从散装值在顶部和底部的界面层的薄膜将被量化。界面性质的改善或退化将与其他测量参数相关联，这些参数变化是为了与动态平均场理论合作确定每个因素的贡献。该项目的重点是比较表面和界面附近的理论和实验深度相关特性，预计将为磁性薄膜的特性提供有价值的见解，并帮助回答有关LSMO复合氧化物表面和界面处磁性表现的主要影响因素，可调应变对LSMO薄膜特性的影响，强关联体系界面性质的一般行为。这些结果可以预期允许优化材料选择和参数，用于各种磁性应用，如计算机存储器，磁传感和能量收集。该项目将支持博士生在先进的真空沉积，理论和表征技术的教育，这已被证明是在学术和技术环境中生产性科学职业的优秀培训。

Nontechnical Abstract:Surfaces of materials have different properties than bulk. Such differences can be manipulated, eliminated or enhanced to improve desired properties and create better, more useful devices. This work focuses on a class of magnetic thin films which are hoped to provide wide array of future applications in computing, electronics and even power generation. A strong collaboration of theory and experiment will benefit the quality of planned effort by providing a way to describe the observations theoretically and build models of observed variations of material properties as a function of depth. This project will support the education of PhD students in advanced vacuum deposition and theoretical and characterization techniques; a proven approach providing excellent training opportunities resulting in productive scientific careers in academic and technology settings. The expected increased physical understanding of magnetism and interfacial properties in thin films from these studies will be particularly relevant to technological applications which incorporate thin magnetic films, such as magnetic recording, spin generation, spin manipulation and/or spin detection. An improved understanding of surface and interface properties will allow smaller devices using less materials, higher energy efficiency and faster communication.Technical Abstract:Magnetic and other properties at surfaces and interfaces are often different from the bulk, which can have significant impact on technologies relying on these properties. To develop enhanced interfaces and potentially new interfacial phenomena, strong competition is favorable. Strongly correlated oxides, with their competition between charge, spin and orbital degrees of freedom offer many promising systems that may allow these tunable parameters. This project will study strongly correlated magnetic LaxSr1-xMnO3 (LSMO) thin films, which have been widely proposed for applications such as tunnel junctions and solid oxide fuel cells. Using scanning transmission electron microscopy and newly developed depth-dependent x-ray absorption analysis to model the magnetization and other properties with depth, the deviation of these parameters from bulk values at both the top and bottom interfacial layers of the thin film will be quantified. Improvements or degradation in the interfacial properties will be linked with the other measured parameters that vary in order to determine in collaboration with dynamical mean field theory the contribution from each factor. The project's focus on comparing the theoretical and experimental depth-dependent properties near surfaces and interfaces is expected to provide valuable insight into the properties of magnetic thin films and help answer questions about the primary contributing factors to the manifestations of magnetic properties at LSMO complex oxide surfaces and interfaces, the effect of adjustable strain on LSMO thin film properties, and general behaviors of interfacial properties in strongly correlated systems. These outcomes can be expected to allow optimization of both material choice and parameters for various magnetic applications such as computer memory, magnetic sensing and energy scavenging. The project will support the education of PhD students in advanced vacuum deposition, theoretical and characterization techniques, which have been proven to be excellent training for productive scientific careers in academic and technology settings.