Physics & Astronomy Colloquium

3:30 PM, Friday, September 22, 2006

Room 155, Chem-Phys Building

Dr. Gang Cao

Department of Physics and Astronomy
University of Kentucky

``4d and 5d Transition Metal Oxides: A New Frontier of Materials Research''

A primary characteristic of the 4d- and 5d-electron elements is that their d-orbitals are more extended compared to those of their 3d-electron counterparts. Stronger p-d electron hybridization and electron-lattice coupling, along with reduced intra-atomic Coulomb interaction U, are thus anticipated in these systems. Consequently, the 4d- and 5d-transition metal oxides have comparable U and bandwidth W, and are on the border between metallic and insulating behavior. Any small perturbations can thus induce drastic changes in the ground state. While these systems exhibit nearly every collective state known for solids, the novelty of them is highlighted by a wide array of intriguing phenomena that are rarely found in other materials. In this talk, results of our transport and thermodynamic studies on new materials involving ruthenium, rhodium and iridium will be presented and discussed with an emphasis on magnetic phenomena such as quantum criticality, colossal magnetoresistance, and geometrical frustration.

Refreshments will be served in CP 179 at 3:15 PM