Ballistic Electron Emission Microscopy and Spectroscopy of Magnetic Multilayers

w：\awards\awards96\*.doc 9632780第一个 本计画的目标是了解自旋相关的电子在交替磁性与磁性材料组成的金属多层膜中的传输与散射。实验使用连续的磁性层作为“偏振器”和“分析器”，外部磁场控制它们的相对取向。 使用低温扫描隧道显微镜，不同的光谱检测通过偏振器/分析器对传输的弹道电子电流，或在多层的场依赖态密度。 这些是第一次详细研究自旋相关的散射在金属和次表面界面的电子能量在+5电子伏的费米能量。他们解决的问题的重要性，为理解振荡 交换耦合和巨磁电阻比，已观察到的磁性多层膜。 这个项目解决了理解“磁性多层膜”的性质的重要问题。这些薄膜具有交替的磁性和磁性层，每个层通常为2纳米厚。 因为这些人造材料展现出一种“巨大”的 磁阻比，它们具有 已经 在超小型和敏感的磁场传感器中找到了应用（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理解。 这些实验使用低温扫描隧道显微镜的光谱能力来获得纳米长度尺度上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. ***