Magnetic dipole imaging by scanning magnetic microscope

A reconstruction technique to evaluate residual magnetic fields and simulate magnetic images due to dipole distribution in ferromagnetic samples has been proposed in connection with a scanning magnetic microscope based on a high-T(c) superconducting quantum interference device (SQUID). We have extended the expression of a point magnetic dipole to represent spatially extended sources and the generated magnetic field has been compared with experiments. In particular, a recently installed scanning SQUID magnetic microscope (model 770 by Tristan Technology) has been used. Magnetic maps obtained at different sample-to-sensor distances and in several configurations have been compared with simulations. With this aim, ferromagnetic rod samples have been modeled as extended magnetic dipoles close to the sensor. Excellent agreement has been obtained, confirming the efficiency of the proposed technique. Such an imaging technique has been demonstrated to be an easy-to-handle tool to identify dipole configurations producing a specific magnetic image.