Magnetic, Electronic, and Structural Development in Atomic Clusters

9731592 Bloomfield这个研究项目研究孤立原子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块状材料的理解联系起来。由于它们的低维度，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深入了解。在这个程序中，团簇是在激光为基础的源和研究与分子束技术。采用施特恩-格拉赫光束偏转法对磁结构进行了探测，研究了局部力矩系统中的表面增强磁化、表面和形状诱导磁各向异性以及自旋倾斜等效应。该程序还搜索额外的磁性有序簇通常非磁性元素和合金。用阴离子光解离光谱研究了团簇电子结构。这项工作着眼于团簇大小，组成，形状和温度对(1)这些系统中的电子容纳模式，(2)它们的结构和电子相，以及(3)它们的电子激发态的影响。这个研究项目检查比原子本身稍大的材料颗粒的磁性和电子特性，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越来越小，它们的尺寸已经不能再被简单地看作是大物体的小版本了。相反，这些微小的设备必须部分地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。通过研究原子簇中的磁性，该研究项目正在了解固体中的磁性是如何从分子结构发展而来的，并为最终产生磁性存储介质绘制出可能性。在研究电子和空间结构的过程中，这个项目正在探索接近原子尺度的绝缘体和金属的世界，并在它们变得如此之小以至于几乎所有的原子都在表面时检查它们的行为。＊＊＊

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. ***