A kind of metal detector used in geophysical surveying to detect primary metals and, under favourable conditions, shallowly buried features. A magnetic field is generated by a transmitted pulse in order to induce a magnetic moment in the soil and its contents. The magnetic moment continues to increase in magnitude while the field is maintained. When the magnetic field is removed at the end of the transmitted pulse, a small magnetic moment remains and the subsequent decay of this so‐called magnetic viscosity induces a voltage in a receiver coil. The voltage induced is broadly proportional to the magnetic susceptibility of the soil and any materials in it at the point sampled. The technique is not very widely used.