Revealing Exchange Interactions in Magnetic Bilayers at the Atomic Scale

该项目由材料研究部电子和光子材料计划(EPM)和凝聚态物理计划(CMP)联合资助。技术描述：该项目旨在探索和揭示原子尺度下磁性双层系统中的磁交换相互作用机制。它包括三个研究部分：1)通常非磁性材料与磁性层接触时的磁极化率；2)交换偏置的基本来源；3)磁性双层系统中的长程相互作用的影响。在所有情况下，空间变化都是特别令人感兴趣的，作为交换作用的函数，交换作用可能强烈地依赖于空间变化。采用分子束或脉冲激光外延技术制备双层超薄膜。在材料合成步骤之后，利用自旋极化扫描隧道显微镜技术对双层体系进行了研究。通过使用磁探针尖，从恒流图像和差分电导数据中同时获得原子尺度下的磁、电子和地形信息。与理论计算相比，这些结果可以为这些重要的和技术上有影响的材料系统的基本原理提供新的见解。非技术描述：为了使设备越来越小型化，对基础物理有基本的了解是至关重要的。一种称为交换耦合的普遍现象是当今最先进的磁性设备技术的核心。一个重要的例子是交换偏置，即两种类型的薄磁层--铁磁层和反铁磁层--直接接触。这可能会导致一种称为磁滞位移的独特行为，并增加一个称为矫顽力的参数。这些效应是现代高密度读取头技术的基础；尽管有许多理论可以解释它，但它的最终起源仍然是一个谜。在这个项目中，通过使用具有原子尺度分辨率的磁敏探测器技术，科学家们的目标是揭开交换耦合效应，并有望提供对未来磁性技术产生重要影响的新见解。该项目还旨在为从K-12到博士水平的学生提供关键的教育和外展机会。本科生和研究生都是该项目所有阶段的积极参与者，他们都在成为未来的科学家。与此同时，开展了两项新的外展活动--一项是在K-12学校演讲，另一项是K-12学生的课外、大学校园活动--其总体目的是激励俄亥俄州东南部的孩子们追求科学和工程职业道路。

This project is jointly funded by the Electronic and Photonic Materials Program (EPM) and Condensed Matter Physics Program (CMP) in the Division of Materials Research (DMR).Technical Description: This project is aimed at exploring and revealing magnetic exchange interaction mechanisms in magnetic bilayer systems down to atomic scale. It includes three research components: 1) magnetic polarizability of normally non-magnetic materials in contact with magnetic layers; 2) fundamental origins of exchange bias; and 3) effects of long-range interactions in magnetic bilayer systems. In all cases, spatial variations are of particular interest, as a function of which exchange interactions may depend strongly. Bilayer ultra-thin films are prepared using either molecular beam or pulsed laser epitaxy. Following the materials synthesis step, the bilayer systems are studied using the technique of spin-polarized scanning tunneling microscopy. Magnetic, electronic, and topographical information down to the atomic scale is obtained simultaneously from constant current images and from differential conductance data by using magnetic probe tips. Comparing to theoretical calculations, the results can provide new insights into the fundamentals of these important and technologically impactful material systems.Non-technical Description: In order to miniaturize devices further and further, it is critical to have fundamental understanding of the underlying physics. A general phenomenon called exchange coupling is at the heart of the most advanced magnetic device technologies today. An important example is exchange bias, in which two types of thin magnetic layers - a ferromagnetic and an antiferromagnetic layer - are put into direct contact. This can result in a unique behavior called hysteresis shift and increases in a parameter called the coercivity. These effects underlie modern high-density read head technology; but despite many theories designed to explain it, its ultimate origins remain a mystery. In this project, by employing a magnetically sensitive probe technique having atomic-scale resolution, scientists aim to unravel exchange coupling effects, and hopefully to provide new insights which can have important impacts on future magnetic technologies. The project also aims to provide key educational and outreach opportunities for students ranging from K-12 through the Ph.D. level. Both undergraduate and graduate students are active participants in all phases of the project, on their way to becoming future scientists. At the same time, two new outreach activities are undertaken - one involving presentations in K-12 schools, the other involving after-school, university-campus activities for K-12 students - whose overall purpose is to inspire the children of Southeast Ohio to pursue science and engineering career paths.