Spin-Polarized Scanning Tunneling Microscopy (SPSTM) opens important possibilities for studies of magnetic nanostructures. It is a very exciting extension of the STM technique that could allow magnetically-sensitive microscopy to extend into sub-nm resolution. The ability to observe magnetism on the level of groups of atoms and individual atoms is a very exciting goal from the fundamental research point of view. In practice, the ability to image nanometer scale magnetic structures becomes important as individual bits in magnetic storage (e.g., hard drives) become smaller in order to achieve higher recording densities.
Scanning-probe microscopies revolutionized surface science research, providing the possibility of direct observation and manipulation of atomic structure of surfaces with sub-nm precision. Can this awesome power be extended into studies of magnetic properties? Spin-polarized scanning tunneling microscopy proposes to use spin-dependent tunneling to do just that. Here details and preliminary results are reviewed for the two currently developed approaches: magnetic (metallic) tips and optically pumped GaAs tips. Each of the two techniques is beneficial for a specific class of measurements and may ultimately achieve atomic resolution.
*Current address: Physics Department, University of Maryland, College Park
This review was written in 1997 as a "practice" paper for a Physics presentation class at the University of Wisconsin, Madison. Even in this relatively new field, a comprehensive survey would be beyond the scope of the project, so this review was intended as a look at the main approaches to SPSTM. In a decade since the review was written, there have been important developments in the spin-polarized and magnetic microscopy. The information in the review is thus no longer current, but the work described therein represents important milestones on the quest for SPSTM with atomic resolution.
Chapter on Spin-Polarized STM in
"Scanning Probe Microscopy - Analytical Methods" (Springer NanoScience and Technology series)
edited by Prof. Roland Wiesendanger.