Ward Plummer, University of Tennessee and ORNL

I will begin this presentation by discussing the societal needs for new materials for the 21st century, driven by our need for energy, preserving our environment and responding to the presidents American Competitiveness Initiative. The time frame needed requires a revolutionary-- not evolutionary--approach to the design and discovery of new materials. I will then compare and contrast the Einstein reductionary philosophy with Andersen's complexity and emergent phenomena philosophy.

I will use magnetism in nanostructured materials to illustrate the Andersen viewpoint, stressing the need for Discovery-Based Research. This presentation will describe unexpected magnetic properties observed in artificially nano-structured materials. Time permitting I will discuss five different examples. 1) Two-dimensional arrays of nano-dots of Fe can be fabricated with controlled density and size. They exhibit "superferromagnetic" behavior instead of the expected superparamagnetic ordering. 2) Stacked arrays of these dots show the transition from ferromagnetism to a pseudo spin-glass accompanying the 2-dimensional to 3-dimensional cross over. 3) The use of "subsurfactant" epitaxy growth to generate a dilute magnetic semiconductor with ~0.25% interstitial Mn in Ge. The ferromagnetic ordering temperature is TC > 440K. All of these examples can't be explained with conventional pictures of magnetic coupling. 4) Magnetic nanoparticles in polymers to create and efficient, flexible photovoltaic device, 5) Size filtered Fe nanoparticles as a way of passively targeting brain tumors.