"Neutron Scattering, Transport, and Dilatometry Measurements of Magnetic Materials"

我们现代技术的很大一部分是基于材料及其特性，例如，微处理器、计算机硬盘驱动器、发光二极管。这些材料允许成本效益高，可靠的设备。有用的属性通常基于系统中的一些基本物理。以计算机硬盘驱动器为例，驱动器的很小一部分充当永磁体，其极性可以通过写磁头切换，并通过读磁头以极高的速度测量。拟议中的研究重点是磁性材料，它们以多种方式排列，通常比计算机硬盘驱动器更奇特。在这些情况下，我们仍然试图弄清楚排序的细节以及它是如何发生的。了解这些系统中的磁性是本研究的主要目标。从基本观点来看，这很重要，但对于可能的应用程序也是如此。在许多情况下，这些体系可以在温度、磁场或添加掺杂剂的很小变化下经历很大的有序变化。在其中一种材料中，磁性几乎可以通过形成成对的相反排列的磁铁而消失。在另一种情况下，磁性的变化会使导电性发生很大变化，就像磁性开关一样。另一种材料具有螺旋型的顺序，这种顺序与没有任何电阻的材料有关。这项研究涉及中子散射，它提供了大量关于原子或电子尺度上的磁性的信息，但在非常大的设备上进行。也有电阻测量和使用敏感设备直接测量样品膨胀。

A very large fraction of our modern technology is based on materials and their properties, e.g., microprocessors, computer hard drives, light-emitting diodes. These materials allow for cost-effective, reliable devices. The useful properties are often based on some fundamental physics in the system. In the case of computer hard drives, a very small part of the drive acts as a permanent magnet, whose polarity can be switched by a write head and measured by a read head at extremely high speeds. The proposed research focuses on magnetic materials, that order in a large number of ways, often in a way that is more exotic than the computer hard drive. In these cases, we are still trying to figure out the details of the ordering and how it comes about. Understanding the magnetism in these systems is the primary goal of this research. This is important from a fundamental viewpoint, but also for possible applications. In many cases, these systems can undergo large changes of ordering with very small changes in temperature, magnetic field, or by adding dopants. In one of the materials, the magnetism can almost disappear by forming pairs of oppositely aligned magnets. In another, a change in magnetism makes a big change in the electrical conductivity, like a magnetic switch. Another material has a spiral type of order that is related to materials that do not have any electrical resistance. The research involves neutron scattering, which gives a lot of information about magnetism on an atom by atom or electron by electron scale, but is carried out at very large facilities. There are also measurements of the electrical resistance and direct measurements of sample expansion using sensitive equipment.