Experimental Studies of Surface and Interface Magnetism by Spin Polarized Electron Techniques

本研究项目涉及磁性表面低能电子的自旋散射，以及铁磁性和反铁磁性材料界面的磁性结构。磁振子在磁性材料中低能电子散射中的作用在很大程度上尚未被探索。一个高分辨率的电子能量损失谱仪（EELS）将与一个自旋极化电子源相结合来测量这些自旋相关的激发。在铁磁/反铁磁界面上的交换耦合是当前在一系列背景下感兴趣的。例如，原子尺度的粗糙度可以导致挫折，并可以驱动铁磁薄膜的磁重定向转变。本项目将通过磁显微镜研究超薄铁磁薄膜的温度依赖微观磁性结构，并通过STM和AFM进行互补结构表征。研究生将接受最先进的样品制备和表征技术的培训，为他们在学术、政府或工业实验室的研究职位做好准备。基于磁性纳米结构中自旋相关输运的电子器件的一个新领域正在兴起，其名称为“自旋电子学”。在这些器件中，电性能取决于层厚为纳米级的磁性材料的磁性结构。在这些磁性材料中，电子可以通过激发材料中的自旋波（磁振子）而失去能量。这些过程，目前在很大程度上尚未在实验中探索，在确定材料的电学性质方面可能非常重要。在这个项目中，电子将从磁性表面散射，并研究它们的能量损失。使用自旋极化电子束可以区分磁激发和非磁激发。在不同磁性材料的界面处，磁性可以由材料之间的磁耦合来决定。这可以导致超薄磁性薄膜的不寻常的磁性。这些影响很大程度上取决于界面质量，例如原子尺度的粗糙度。该计划将结合磁显微镜和STM来研究与反铁磁衬底接触的磁性薄膜中形貌和微磁结构之间的相互作用。学生将接受尖端材料制备和先进测量技术的培训，为材料和应用物理的学术或工业研究做好准备。

This research program is concerned with the spin dependent scattering of low-energy electrons from magnetic surfaces, and with the magnetic structure at interfaces of ferromagnetic and antiferromagnetic materials. The role of magnons in low-energy electron scattering in magnetic materials is largely unexplored. A high-resolution electron energy loss spectrometer (EELS ) will be built and combined with a spin polarized electron source to measure these spin dependent excitations. The exchange coupling at ferromagnetic/antiferromagnetic interfaces is of current interest in a range of contexts. For example, atomic scale roughness can lead to frustration and can drive magnetic reorientation transitions of the ferromagnetic film. This project will study the temperature dependent microscopic magnetic structures in ultrathin ferromagnetic films by magnetic microscopy and complementary structural characterization by STM and AFM. Graduate students will be trained in state of the art sample preparation and characterization techniques that prepare them for research positions in academic, government or industry laboratories.%%%A new field of electronic devices based on spin dependent transport in magnetic nanostructures is currently emerging under the name of "spintronics". In these devices the electrical properties depend on the magnetic structure of magnetic materials with layer thickness of nanometers. In these magnetic materials, electrons can lose energy by exciting spin waves (magnons) in the material. These processes, currently largely unexplored experimentally, are potentially very important in determining the materials' electrical properties. In this project, electrons will be scattered off magnetic surfaces and their energy losses studied. Use of a spin polarized electron beam allows one to distinguish between magnetic and non-magnetic excitations.At interfaces of different magnetic materials the magnetism can be dominated by the magnetic coupling between the materials. This can lead to unusual magnetic properties of ultrathin magnetic films. These effects depend sensitively on the interface quality, e.g. atomic scale roughness. This program will combine magnetic microscopy and STM to study the interplay between topography and micro-magnetic structure in magnetic thin films in contact with antiferromagnetic substrates. Students will be trained in cutting-edge materials preparation and advanced measurement techniques that prepare them for academic or industrial research in Materials and Applied Physics.