Audio frequency magnetic induction in soils

Soils often possess a measurable magnetic susceptibility, due to the presence of ferromagnetic minerals such as magnetite and maghemite. Sometimes, this susceptibility is appreciably dispersive (frequency and delay time-dependent) because the grains are small enough to approach the thermal agitation limit of superparamagnetism. Dispersion can be important in applied geophysics and related fields like archeology and demining.