Ballistic Electron Emission Microscopy and Spectroscopy of Magnetic Multilayers

9632780首先，这个项目的目标是了解由交替的磁性和非磁性材料组成的金属多层膜中与自旋相关的电子传输和散射。这些实验使用连续的磁层作为“偏振器”和“分析器”，外加磁场控制它们的相对取向。使用低温扫描隧道显微镜，不同的光谱仪要么检测通过偏振器/分析器对传输的弹道电子电流，要么检测多层膜中依赖于场的状态密度。这些是首次详细研究金属中的自旋相关散射，以及在次表面界面上费米能量+5电子伏特范围内的电子能量。它们解决了对于理解在磁性多层膜中观察到的振荡交换耦合和巨磁电阻比的重要问题。%这个项目解决了对理解“磁性多层膜”的性质具有重要意义的问题。这些薄膜具有交替的磁性和非磁性层，每个层通常有两纳米厚。由于这些人造材料表现出巨大的磁电阻率，它们已经在超小型和敏感的磁场传感器中得到了应用(例如，在计算机磁盘驱动器中)。尽管如此，观测到的磁效应的基本基础还没有完全被理解。这些实验利用低温扫描隧道显微镜的光谱能力，在纳米尺度上获得有关磁性多层膜特性的信息。***

w:\awards\awards96\*.doc 9632780 First The goal of this project is to understand spin-dependent electron transmission and scattering in metallic multilayers composed of alternating magnetic and nonmagnetic materials. The experiments use successive magnetic layers as "polarizer" and "analyzer", with an external magnetic field controlling their relative orientation. Using a cryogenic scanning tunneling microscope, different spectroscopies detect either the ballistic electron current transmitted through the polarizer/analyzer pairs, or the field-dependent density of states in the multilayer. These are among the first detailed studies of spin-dependent scattering in metals and at subsurface interfaces for electron energies within +5 electron volt of the Fermi energy. They address issues of importance for understanding both the oscillatory exchange coupling and the giant magnetoresistance ratios that have been observed in magnetic multilayers. %%% This project addresses issues of importance for understanding the properties of "magnetic multilayers". These are thin films with alternating magnetic and nonmagnetic layers, each typically two nanometer thick. Because these man-made materials exhibit a "giant" magnetoresistance ratio, they have already found applications in ultrasmall and sensitive magnetic field sensors (in computer disk drives, for instance). Still, the fundamental basis for the observed magnetic effects is not fully understood. These experiments use the spectroscopic capabilities of a low- temperature scanning tunneling microscope to derive information about the properties of magnetic multilayers on a nanometer length scale. ***