Reciprocity in magnetic force microscopy

A theoretical treatment for contrast formation in the magnetic force microscope is given which relies on calculation of the force acting on the sample, rather than the more usual method which calculates the force acting on the microscope tip. The equivalence of this reciprocal force method is demonstrated by calculating the theoretical image for longitudinal step and arctangent magnetization transitions in thin-film recording media. The reciprocal force approach leads naturally to unambiguous definitions for the resolution of the magnetic force microscope and it is shown that conventional resolution measures, such as impulse response, line-spread function and step response, used in many other forms of microscopy, may be readily applied to the magnetic force microscope.