Overview
In MFM measurements, the magnetic force between the sample and the tip can be expressed as
where is the magnetic moment of the tip (approximated as a point dipole), is the magnetic stray field from the sample surface, and ยต0 is the magnetic permeability of free space.
Because the stray magnetic field from the sample can affect the magnetic state of the tip, and vice versa, interpretation of the MFM measurement is not straightforward. For instance, the geometry of the tip magnetization must be known for quantitative analysis.
Typical resolution of 30 nm can be achieved, although resolutions as low as 10 to 20 nm are attainable.
Read more about this topic: Magnetic Force Microscope