A reciprocity-based approach to understanding magnetic force microscopy

The process of image formation in a magnetic force microscope is described in terms of the 'reciprocal' force acting on the sample, rather than the more usual method that calculates the force acting on the microscope tip. The two forces are, according to Newton's third law, equal but opposite. It is shown that the reciprocal force approach allows the role of the microscope tip in the imaging process to be revealed explicitly in both spatial and spatial frequency domains. In particular, the system transfer function is shown to comprise a product of the well known Wallace loss factors used to describe inductive readout in magnetic recording systems.