An Investigation of Magnetic Reversal at Almost the Nanoscale
Speaker: E. Dan Dahlberg, Director of the Magnetic Microscopy Center, College of Science and Engineering Distinguished Professor, and Professor of Physics, University of Minnesota
Date: September 8, 2011
Time: 5:00 p.m.
Location: Sun Room, Memorial Union
Abstract: One of the current frontiers in magnetism is to understand the domain structure and the magnetization reversal in nanometer sized particles. Explorations at these length scales have been aided by the development of new magnetic imaging techniques, one of which is the magnetic force microscope (MFM), a variant of the atomic force microscope. Dahlberg and his team have utilized the high resolution MFM (30 nanometers) they developed to increase their fundamental understanding of magnetism on this length scale. Dahlberg will discuss the field induced magnetic reversal in stadia shaped particles on the order of hundreds of nanometers wide and about twice that in length. In general, for the small aspect ratio stadia (length to width ratio), the magnetization reverses by the formation of a single vortex and its propagation down the length of a stadium (when the fields are applied perpendicular to the long axis). The surprising discovery is the importance of virtual particles (vortex-antivortex pairs) creation and annihilation in the magnetic reversal in larger aspect ratio stadia.
Speaker biography: Dahlberg is the director of the Magnetic Microscopy Center, a College of Science and Engineering Distinguished Professor and professor of physic at the University of Minnesota. His current research interests include the magnetic properties of magnetic thin films, multilayers, and tunnel junctions. His honors include an Alfred P. Sloan Foundation Research Fellowship, Fellow of the American Association for the Advancement of Science, Fellow of the American Physical Society, George Taylor/ IT Alumni Society Award for Teaching, Distinguished Alumnus for the College of Science at the University of Texas at Arlington, University of Minnesota Outstanding Community Service Award, George Taylor Distinguished Service Award, and elected Distinguished Lecturer for Institute of Electrical and Electronics Engineers (IEEE) Magnetics Society. Dahlberg received his bachelor’s and Master of Arts degrees in physics from the University of Texas at Arlington, and he received his Master of Science and PhD degrees in physics from UCLA.
*Lecture cosponsored by Committee on Lectures (funded by GSB)