Scanning Hall Probe Microscopy of Superconducting Systems

w：\awards\awards96\num.doc 9701532字段 这个实验研究项目的重点是使用最先进的低温扫描霍尔探针显微镜，具有高空间（1微米）和时间分辨率的II型超导体的不寻常的磁特性。第一个要研究的系统是一个大型的介观超导环阵列。磁 时刻 在 等 环 可以 耦合“反铁磁”，通过纯粹的磁相互作用，这已经在初步实验中观察到。 更清洁的阵列将被研究，以寻找真正的长程有序。 该显微镜还将用于研究随机和周期性钉扎超导体中涡旋的静态和动态特性。在随机的情况下，主要的兴趣是在空间分辨 旋涡动力学 在 一 无序势，当由磁场或施加的电流强烈驱动时，期望获得关于脱钉转变的新信息。 随着周期性钉扎，实验将探讨两个竞争的长度尺度的变化的后果：涡涡间距和钉扎站点之间的距离。 %这个 实验研究项目探索 的 超导体的磁性，特别注意磁通量在外部磁场或通过超导体的电流推动下如何穿过超导体。 由于正是这种磁通量运动通常导致超导体的标志--完美导电性的丧失，因此对这些问题的更深入理解可能会导致技术应用的改进 超导体，如在发电和传输。 磁通运动将使用强大的新技术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，它可能会在许多领域（如硬盘技术）中使用，这些领域对磁场的局部结构感兴趣。 这项研究的结果可能包括不寻常的新效果或可能在技术中找到新应用的材料。这个研究项目是跨学科的性质，涉及研究生谁将得到良好的培训，进入行业，政府或教育职位。 ***

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. ***