Multifrequency electromagnetic response of a magnetically permeable cover-target system

Multifrequency EM response of a cover-target system represented by two concentric spherical shells has been analyzed, theoretically, for uniform field excitations. Some numerical results have been presented to show the effects of changing (i) the product of conductivity and thickness and (ii) the magnetic permeability values of the inner or outer shell. It is found in multifrequency EM measurements that (i) the imaginary component of the response factor shows the maximum sensitivity to the changes in physical and geometrical properties of the cover and/or target bodies; (ii) a magnetic shell is reflected earlier than the corresponding nonmagnetic ones. The study may find relevance in delineating (i) pyrhotite possessing ferromagnetic properties and (ii) thin conducting deposits separated by resistive formations.