Investigation of the Magnetic Anistropy and Magnetic Phase Transition using Stepped Surfaces

这是一项磁学领域的基础研究项目。本文主要研究了人工结构磁性薄膜的性能。目的是了解晶格对称破缺对这些材料磁各向异性的作用。磁性各向异性是材料磁性的主要决定因素，特别是作为磁性存储介质的候选材料。在受控表面上，纳米大小的原子台阶将被创建，以打破四重旋转对称，从而在薄膜平面内诱导单轴磁各向异性。这种步进诱导的磁各向异性及其对二维磁相变的影响将作为步进密度的函数进行系统的研究。该项目的一个新颖方面是采用弯曲基板作为连续控制步长密度的可能手段。所有样品将通过分子束外延（MBE）生长，并通过反射高能电子衍射（RHEED），低能电子衍射（LEED），俄歇电子能谱（AES）和扫描隧道显微镜（STM）进行表征。利用表面磁光克尔效应（SMOKE）技术原位测量薄膜的磁性能。这是磁学领域的一项基础研究项目。随着信息存储技术的飞速发展，需要在原子尺度上理解材料的磁性行为。本提案的目标是通过在原子尺度上限制磁体的大小来更深入地了解磁体的磁各向异性将如何受到影响。为了实现这一目标，将使用定义良好的原子步骤来打破连续表面的旋转对称性。然后系统地研究了步进诱导磁各向异性及其对二维磁相变的影响，并将其作为步进密度的函数。最先进的技术，如分子束外延（MBE）和扫描隧道显微镜（STM）将应用于该项目，以在原子尺度上制造和表征薄膜。该项目的成功不仅对二维磁学的理解具有重要意义，而且对开发实际应用的新型磁性器件也具有重要意义。＊＊＊

Qiu 9805222 This is a fundamental research project in the field of magnetism. The research is focused on the properties of artificially structured thin magnetic films. The objective is an understanding of the role of lattice symmetry-breaking on the magnetic anisotropy in these materials. The magnetic anisotropy is a major determinant of the magnetic properties of the materials, particularly there properties as candidates for magnetic storage media. Nanometer-sized atomic steps on a controlled surface will be created to break the four-fold rotation symmetry to induce a uniaxial magnetic anisotropy within the film plane. This step- induced magnetic anisotropy and its effect on the two-dimensional (2D) magnetic phase transition will be investigated systematically as a function of the step-density. A novel aspect of the project is to employ a curved substrate as a possible means of controlling the step-density in a continuous way. All samples will be grown by Molecular Beam Epitaxy (MBE) and characterized by Reflection High-Energy Electron Diffraction (RHEED), Low-Energy Electron Diffraction (LEED), Auger Electron spectroscopy (AES) and Scanning Tunneling Microscopy (STM). The magnetic properties of the films will be measured in situ by Surface Magneto-Optic Kerr Effect (SMOKE) technique. %%% This is a fundamental research project in the field of magnetism. Rapid development in the information storage technology demands an understanding of the magnetic behavior of materials at the atomic scale. The goal of this proposal is to gain a deeper understanding on how the magnetic anisotropy of a magnet will be affected by limiting the size of the magnetic at the atomic scale. To realize this goal, well-defined atomic steps will be used to break the rotation symmetry of the continuous surface. The step induced magnetic anisotropy and its effect on the 2D magnetic pha se transition will then be systematically investigated as a function of the step-density. State-of-the-art techniques such as the Molecular Beam Epitaxy (MBE) and Scanning Tunneling Microscopy (STM) will be applied to this project to fabricate and characterize the thin films at the atomic scale. Success of this project will be important not only to the understanding of two-dimensional magnetism, but also to the development of new magnetic devices for practical applications. ***