Magnetic, Electronic, and Structural Development in Atomic Clusters

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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. ***