AN INVERSE PROBLEM FOR THE AC MAGNETIC FORCE MICROSCOPY OF SUPERCONDUCTORS

A basic inversion problem for the magnetic force microscopy (MFM) of a semiinfinite superconductor in the Meissner state is formulated. ac D etection is assumed, with the MFM tip oscillating at angular frequency omega. The coupling of all electrodynamic fields is treated, includin g a normal-current density in the superconductor. Under certain assump tions on the tip and superconductor geometry, a unique penetration dep th lambda(z) can be recovered from one-dimensional force gradient meas urements. This development opens new possibilities for the nondestruct ive evaluation of superconducting crystals and films.