*****NON-TECHNICAL ABSTRACT**** Metal clusters, composed of a few to a few hundred atoms, are prototypical nanoscale objects. Their intrinsic properties are studied in molecular beams in a vacuum where they are not affected by supporting structures. Many interesting properties result when the motion of the conduction electrons in metals becomes correlated. The best known of these are ferromagnetism and superconductivity. This project will use molecular beam studies to trace the evolution of these properties as a function of cluster size. For example, the magnetic properties of an iron cluster composed of 5 atoms are different than those of a cluster with 500 atoms, and both exhibit recognizable bulk magnetic features. Insight into these evolutionary trends in magnetism will help in designing novel nano-magnetic materials, which are important for the recording industry. The students participating in this research will learn scientific concepts and state-of-the-art techniques, which will prepare them for careers in academic, industrial, or governmental research. In addition, outreach to high school science teachers is planned. This project is supported by the Condensed Matter Physics program in the Division of Materials Research and the Atomic, Molecular, and Optical Physics program in the Physics Division.
This individual investigator award supports a project using state of the art low-temperature molecular beam methods developed at GIT to measure properties of a wide variety of metal clusters as a function of mass and temperature (T=10-300 K). Support-free clusters at very low temperatures are particularly important, not only because their properties can be accurately measured with precise knowledge of their size, but also because a relatively large fraction of the clusters in the beam are frozen in their quantum mechanical ground states. This virtually unexplored state of matter provides a unique opportunity to investigate electronic properties and electronic phase transitions involving ferromagnetism, ferroelectricity and superconductivity. The relationship of the ferroelectric phase transition to superconductivity in Nb, V, and Ta, clusters will be examined. In addition cluster ferromagnetism will be investigated. In particular for cobalt clusters a ground state with 2 Bohr magnetons per atom and an electronically excited state with about 1 Bohr magneton per atom has been observed. This observation suggests a mechanism for the evolution of molecular magnetism to bulk itinerant ferromagnetism. The students involved with this research will learn scientific concepts and state-of-the-art techniques, which will prepare them for careers in academic, industrial, or governmental research. In addition, outreach to high school science teachers is planned. This project is supported by the Condensed Matter Physics program in the Division of Materials Research and the Atomic, Molecular, and Optical Physics program in the Physics Division
