Magnetic domain imaging using orthogonal fluxgate probes

This article presents an application of a miniature orthogonal fluxgate magnetometer to magnetic domain imaging of coated grain-oriented silicon steels. The method is based on a common technique which maps stray magnetic fields emerging from the surface of the silicon steel. An orthogonal fluxgate made of a thin amorphous wire core is bent in a J-shape so that it may work as a gradiometer, in which the longer leg of the J-shaped wire core is made sensitive to stray magnetic fields whereas the shorter one is effectively located at a distance from them. Experiments were carried out with a thin Co-based amorphous wire used as a wire core and a highly grain oriented silicon steel as a sample on which the domain refinement by laser irradiation is made. Well-defined stripe domains with some spike domains, and grain boundaries were clearly imaged with this method without any assisting magnetic field to enhance stray magnetic fields.