The Iterative Process of Scientific Exploration: Effects of Electrical Current in Nanomagnetic Systems

Prof. Sergei Urazhdin
Dept. of Physics, Emory University

Abstract: In the iterative process of scientific exploration, experimental observations are generalized into hypotheses, leading to predictions subsequently tested in experiments, and so on. In nanoscience and nanotechnology, this process is complicated by the indirect nature of observations, often making it challenging to confirm or disprove scientific predictions. I will illustrate this process with the studies of the effects of electrical currents on nanomagnetic systems. They started with a theoretical prediction, 20 years ago, that spin-polarized current can induce magnetization precession or reversal, which can be utilized in multiple applications from hybrid memory to microwave generation and logic. While the subsequent experiments confirmed this idea, we have found that the predicted precession generally does not occur. I will show how the experimental observations can be explained by the nonlinear dynamical properties inherent to the magnetic systems. Furthermore, I will show a critical re-examination of the theory underlying the current-induced phenomena in nanomagnetic systems reveals quantum effects that are conventionally assumed to be negligible at length scales above a few nanometers, but turn out to provide significant contributions to electron transport and magnetization dynamics even in 100 nanometer-scale systems.

Bio: Prof. Urazhdin received a PhD in Physics from Michigan State University in 2002. His PhD work focused on the discovery of surface states in narrow gap semiconductors, which became later known as topological insulators. After postdoctoral research in nanomagnetism at Johns Hopkins University, in 2005 he joined the Physics Department at West Virginia University, and in 2011 moved to Emory University. Dr. Urazhdin received an NSF CAREER Award in 2007 and a Cottrell Scholar Award from the Research Corporation in 2008. His research mainly focuses on the dynamical properties of nanomagnets, electrical current-induced effects in magnetic systems, and electron spin physics.