Magnetic Force Microscopy

Principle of MFM In magnetic force microscopy (MFM), the magnetic stray field above a very flat specimen, or sample, is detected by placing a small magnetic element, the tip, mounted on a cantilever spring very close to the surface of the sample (Figure 1). Typical dimensions are a cantilever length of 200 mm, tip length of 4 mm, and diameter of 50 nm and a distance of 30 nm from the surface. The force on the magnetic tip is detected by measuring the displacement of the end of the cantilever, usually by optical means. The forces measured in typical MFM applications are in the order of 30 pN, with typical cantilever deflections in the order of nanometers. An image of the magnetic stray field is obtained by slowly scanning the cantilever over the sample surface, in a raster-like fashion. Typical scan areas are from 1 up to 200 mm, with imaging times in the order of 5–30 min.