Magnetism, Electronic Structure, and Dynamics in Atomic Clusters

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

This experimental research project uses small clusters of atoms to examine the development of several bulk characteristics and phenomena-magnetism, structural defects, and phase transitions-out of molecular properties. Its main thrusts are in magnetic ordering in ferro- and ferri-magnetic particles and in ultrafast ion and electron dynamics in salt systems. The magnetic component seeks to address numerous theoretical uncertainties in the spin ordering of low-dimensional systems. Predictions of enhanced ferromagnetic ordering and even elevated Curie temperatures have been predicted in one- and two-dimensional systems, and small particles, with their large fraction of surface atoms, are proving to be an excellent laboratory in which to study such effects. Spin-canting and a competition between ferro- and antiferromagnetic orderings have also been examined theoretically and will be studied in this work. The dynamics portion examines the interactions of alkali-halide clusters with light, looking at the roles of various energies-thermal, electronic, vibrational, and rotational-in the finite-system equivalents of heating, cooling, melting, and evaporating. Graduate students participating in this research will receive training that will prepare them for industrial, academic, or government careers in the rapidly developing fields of optical science and engineering and nanotechnology, particularly the emerging fields of magnetic and non-volatile charge-based memory and optical computing. This research uses small collections of atoms to examine connections between the science of individual atoms and molecules and the science of bulk matter. In particular, it studies how bulk magnetic properties emerge from those of the individual atoms that comprise bulk matter and how temperature, melting, and evaporation are related to various dynamic phenomena in small molecules. Both experimental programs involve beams of tiny particles in vacuum, so that those particles are studied in the pristine state of perfect isolation. They are therefore well-suited to address many fundamental questions, including how the magnetic atoms in a material order themselves to retain or cancel their magnetism in larger system, how light energy heats small systems, and how large a particle has to be in order to exhibit such bulk properties and phenomena as temperature, crystal structure, and changes of material phase. This research has close connections with modern magnetic and electronic memory systems and with optical storage and communications. Students in this research program undergo rigorous training in condensed matter, atomic, molecular, and optical physics and are well prepared for careers in industrial or academic science.