This project is jointly funded by the Electronic and Photonic Materials Program (EPM) and Condensed Matter Physics Program (CMP) in the Division of Materials Research (DMR).
This project is aimed at exploring and revealing magnetic exchange interaction mechanisms in magnetic bilayer systems down to atomic scale. It includes three research components: 1) magnetic polarizability of normally non-magnetic materials in contact with magnetic layers; 2) fundamental origins of exchange bias; and 3) effects of long-range interactions in magnetic bilayer systems. In all cases, spatial variations are of particular interest, as a function of which exchange interactions may depend strongly. Bilayer ultra-thin films are prepared using either molecular beam or pulsed laser epitaxy. Following the materials synthesis step, the bilayer systems are studied using the technique of spin-polarized scanning tunneling microscopy. Magnetic, electronic, and topographical information down to the atomic scale is obtained simultaneously from constant current images and from differential conductance data by using magnetic probe tips. Comparing to theoretical calculations, the results can provide new insights into the fundamentals of these important and technologically impactful material systems.
Non-technical Description: In order to miniaturize devices further and further, it is critical to have fundamental understanding of the underlying physics. A general phenomenon called exchange coupling is at the heart of the most advanced magnetic device technologies today. An important example is exchange bias, in which two types of thin magnetic layers - a ferromagnetic and an antiferromagnetic layer - are put into direct contact. This can result in a unique behavior called hysteresis shift and increases in a parameter called the coercivity. These effects underlie modern high-density read head technology; but despite many theories designed to explain it, its ultimate origins remain a mystery. In this project, by employing a magnetically sensitive probe technique having atomic-scale resolution, scientists aim to unravel exchange coupling effects, and hopefully to provide new insights which can have important impacts on future magnetic technologies. The project also aims to provide key educational and outreach opportunities for students ranging from K-12 through the Ph.D. level. Both undergraduate and graduate students are active participants in all phases of the project, on their way to becoming future scientists. At the same time, two new outreach activities are undertaken - one involving presentations in K-12 schools, the other involving after-school, university-campus activities for K-12 students - whose overall purpose is to inspire the children of Southeast Ohio to pursue science and engineering career paths.
