Scanning Hall Probe Microscopy of Superconducting Systems

本实验研究项目主要利用最先进的具有高空间（1微米）和时间分辨率的低温扫描霍尔探针显微镜研究II型超导体的异常磁性。要研究的第一个系统是一个大型介观超导环阵列。这些环中的磁矩可以通过纯磁相互作用“反铁磁”耦合，这在初步实验中已经观察到。在搜索真正的长范围顺序时，将研究清洁数组。该显微镜还将用于研究随机和周期性钉钉的超导体中涡旋的静态和动态特性。在随机情况下，主要的兴趣是在磁场或施加电流的强烈驱动下，在无序势中涡旋的空间分辨动力学，并期望获得关于脱壳跃迁的新信息。在周期性钉钉的情况下，实验将探讨两个相互竞争的长度尺度变化的后果：涡-涡间距和钉钉点之间的距离。这个实验研究项目探索超导体的磁性，特别关注当受到外部磁场的推动或通过超导体的电流时，磁通量如何在超导体中移动。由于这种磁通运动通常会导致失去完美的导电性，这是超导体的标志，对这些问题的深入了解可能会导致超导体技术应用的改进，如在发电和输电方面。通量运动将使用强大的扫描霍尔探针显微镜成像。该仪器的进一步发展是该项目的一个组成部分，它可能会在许多对磁场局部结构感兴趣的领域（如硬盘技术）中找到用途。这项研究的结果可能包括不寻常的新效果或材料，可能会在技术上找到新的应用。这个研究项目是跨学科的，涉及研究生，他们将接受良好的培训，进入工业、政府或教育部门。＊＊＊

w:\awards\awards96\num.doc 9701532 Field This experimental research project focuses on unusual magnetic properties of Type II superconductors using a state of the art cryogenic scanning Hall probe microscope, with high spatial (one micrometer) and temporal resolutions. The first system to be studied is a large array of mesoscopic superconducting rings. The magnetic moments in such rings can couple "antiferromagnetically", via purely magnetic interactions, which have been observed in preliminary experiments. Cleaner arrays will be studied in a search for true long range order. The microscope will also be used to study the static and dynamic properties of vortices in superconductors with both random and periodic pinning. In the random case the primary interest is in spatially-resolved dynamics of vortices in a disordered potential, when strongly driven by either magnetic fields or applied currents, with the expectation of getting new information on the depinning transition. With periodic pinning, experiments will probe the consequences of variations of two competing length scales: the vortex-vortex spacing and the distance between pinning sites. %%% This experimental research project explores the magnetic properties of superconductors, with particular attention to how magnetic flux moves through a superconductur when pushed by an external magnetic field, or by a current passing through the superconductor. Since it is this flux motion which generally results in the loss of perfect conductivity, which is the hallmark of superconductors, a deeper understanding of these issues may lead to improved technological applications of superconductors, as in power generation and transmission. The flux motion will be imaged using the powerful new technique of scanning Hall probe microscopy. The further deve lopment of this instrument, which may find use in many fields (such as hard disk technologies) where the local structure of the magnetic field is of interest, is an integral part of the project. Results from this research may include unusual new effects or materials which may find new application in technology. This research project is interdisciplinary in nature and involves graduate students who will be excellently trained to enter positions in industry, government or education. ***