Magnetic, Electronic, and Structural Development in Atomic Clusters

9731592布卢姆菲尔德这项研究计划研究孤立原子团簇中的磁性和电子结构，目的是将目前对原子和分子的理解与对大宗材料的理解联系起来。由于它们的低维，团簇提供了对表面效应、量子尺寸效应、热弛豫过程以及结构和电子相变的分子起源的洞察。在这个项目中，团簇是在基于激光的光源中制备的，并用分子束技术进行研究。用Stern-Gerlach光束偏转方法研究了表面增强磁化强度、表面和形状感生磁各向异性以及局域磁矩系统中的自旋倾斜等磁结构。该程序还搜索通常非磁性元素和合金的附加磁性有序簇。用阴离子光脱附谱研究了团簇的电子结构。这项工作考察了团簇的大小、组成、形状和温度对(1)这些系统中的电子调节模式，(2)它们的结构和电子相，以及(3)它们的电子激发态的影响。这个研究项目考察了仅略大于原子本身的物质颗粒的磁性和电学性质，以此作为弥合固体和分子之间理解差距的一种方式。随着电子元件和磁存储系统变得更小，它们的尺寸已经不能再被简单地视为较大物体的小版本。相反，这些微小的设备必须在一定程度上被视为复杂的分子系统，量子力学的复杂性、热波动和表面结构改变了它们的行为。通过研究原子团簇中的磁性，这项研究计划正在了解固体中的磁性是如何从分子结构中发展出来的，并正在规划出最终产生磁存储介质的可能性。在研究星系团的电子和空间结构时，这个项目正在探索接近原子尺度的绝缘体和金属的世界，并检查它们的行为，当它们变得非常小，几乎所有的原子都在它们的表面上。***

9731592 Bloomfield This research program examines magnetic and electronic structure in isolated atomic clusters, with the goal of connecting present understandings of atoms and molecules to those of bulk materials. Because of their low dimensionalities, clusters provide insight into surface effects, quantum size effects, thermal relaxation processes, and the molecular origins of structural and electronic phase transitions. In this program, clusters are prepared in laser-based sources and studied with molecular beam techniques. Magnetic structure is probed using the Stern-Gerlach beam deflection method and effects such as surface-enhanced magnetization, surface and shape induced magnetic anisotropy, and spin-canting in local moment systems are studied. This program also searches for additional magnetically ordered clusters of normally non-magnetic elements and alloys. Cluster electronic structure is studied by anion photodetachment spectroscopy. This work looks at the effects of cluster size, composition, shape, and temperature on (1) the modes of electron accommodation in these systems, (2) their structural and electronic phases, and (3) their electronically excited states. %%% This research program examines the magnetic and electronic properties of material particles only slightly larger than atoms themselves, as a way to bridge the gap in understanding between solids and molecules. As electronic components and magnetic memory systems become smaller, they reach sizes at which they can no longer be treated simply as small versions of larger objects. Instead, these tiny devices must be viewed in part as elaborate molecular systems, with the complexities of quantum mechanics, thermal fluctuations, and surface structure altering their behavior. By studying magnetism in clusters of atoms, this research program is learning how magnetism in solids develops from molecular st ructure and is mapping out possibilities for the ultimate generation of magnetic storage media. In its work on electronic and spatial structure in clusters, this program is exploring the world of insulators and metals near the atomic scale and is examining their behaviors when they become so small that nearly all their atoms are on their surfaces. ***