Correlating microstructure with magnetic behavior in nanomagnetic systems with transmission electron microscopy
June Lau
National Institute of Standards and Technology, Gaitherburg, MD
Date: September 21, 2007, Time: 3:30 pm, Location: W122-D3 Engineering Building 1, The University of Houston
Abstract:
In the information age, we have come to depend heavily on nanomagnets (think video ipod and tivo), yet it is increasingly difficult to gain useful information on nanomagnetic systems from bulk magnetometry measurements or even from micromagnetic modeling based on bulk parameters. In addition to the signal-to-noise issues associated with small samples, measuring magnetic properties variation due to grain sizes, defects, edges and surfaces, once considered negligible in the bulk, becomes an intractable problem. However, transmission electron microscope (TEM), given its atomic resolution and magnetic sensitivity, have already begun to elucidate the role of nanoscale defects on the switching behavior of patterned nanostructures. In particular, the subject of switching field distribution is of intense interest for applications such as MRAM and patterned media. Recently, we have determined that the field required to nucleate magnetic vortices in patterned Permalloy arrays is dependent on the edge roughness produced by the lithography process. Additionally, we have identified grains with a particular orientation as a cause to the switching field distribution in patterned Co/Pd nanodots. Many challenges still lie ahead for nanomagnetic microscopy, and we will discuss some of these challenges and the response from the community. The potential payoff, however, is a new way to connect magnetic behavior with microstructure.
