Digital Instruments NANOSCOPE III Magnetic Force Microscope
A more detailed description can be found in IRM Quarterly v. 2, n. 4, Winter 1992-1993.
The Magnetic force microscope (MFM) uses a very fine magnetically-coated tip mounted on a cantilever to measure magnetic force as it is scanned across the surface of a sample. The resolution is high enough to allow imaging the magnetization structure inside domain walls.
Here are links to more details regarding sample preparation