Design of a Magnetic Force Microscope for Imaging Nanoscale Vortex Motion
Jennifer Hoffman

Superconductors have many potential uses, including generation of large magnetic fields and minute sensor arrays for medical diagnostics. These applications are presently limited by the uncontrolled motion of ‘vortices’: swirling cur-rents that contain mag-netic fields within the superconductor. On the other hand, controlled vortex motion presents new opportunities for computing.

Given these challenges and opportunities, it is imperative to gain a better understanding of the dynamics of single vortices. We have therefore designed a new cryogenic magnetic force microscope to detect and measure magnetic forces with 10 nanometer spatial resolution and sub-pico Newton force resolution. The drawing shows the instrument design, with a blow-up of the sample imaging region. The sample sits face-up on the white surface, while a magnetic-tipped cantilever (shown in yellow, just above the sample) is used to measure magnetic forces and to manipulate vortices. The magnetic force results in a deflection of the cantilever, which is measured via a laser beam reflected off the cantilever from behind (the small blue circle). The unique feature of this new imaging tool is the vertical cantilever, which allows direct detection of magnetic forces in the plane of the sample.